Aegismax on Amazon has an awesome UL sleeping bag. $75.00 and only weighs 0.97lbs! I've seen people use them like quilts too, only zip up the bottom footbox and lay over yourself.
https://www.amazon.com/AEGISMAX-Urltra-Light-Sleeping-Three-Season-L200cmW86cm/dp/B00XE2SKG2
AEGISMAX Outdoor Urltra-Light Goose Down Sleeping Bag Three-Season Down Sleeping Bag Mummy Down Sleeping Bag Green L200cmW86cm https://www.amazon.com/dp/B00XE2SKG2/ref=cm_sw_r_cp_apa_aFykBb8XF4V5T
It says in the Q and A that they ship to Australia, I'm not familiar with the difference of amazon in the US and Canada though. That would really suck if it's the case.
Might have to rethink my Sleep system now that I have such a high likelihood of snow pack and or snow storms this early in June. Thinking now something closer to 10 degrees comfort. Thoughts?
AEGISMAX Outdoor Ultra-Light Goose Down Sleeping Bag Three-Season Down Sleeping Bag Mummy Down Sleeping Bag Green https://www.amazon.com/dp/B00XE2SKG2/ref=cm_sw_r_cp_api_glt_fabc_BH011K9EEBQXSFAGF9KK?_encoding=UTF8&psc=1
I'm going to be trying out my Aegismax bag next week when I hike the Loyalsock Trail. I'm expecting highs in the 80s and lows in the 50s, but wouldn't be surprised if it got into the 40s. Aegismax says the comfort zone is +2-8C (35-45F). I tried it out overnight last weekend and was right on the edge of comfort during the coldest hours of the night. I think it was in the low 50s or so, but I didn't have a thermometer. I didn't use a liner, and I was sleeping in my skivvies. I'll admit I was a tad disappointed that the comfort zone wasn't anywhere near 35F, but I know I could improve on that by wearing long underwear and/or using a liner.
The point is it's going to depend on the quality of the bag, your sleeping clothes/liner, and your pad. The latter is very important. The Aegismax is super cheap and super light (under a pound), but relatively low quality. A fleece blanket becomes a viable option when it's warm enough.
As for combining two bags for winter, I can't tell you for sure, but I would imagine that it wouldn't work very well. Sleeping bags work by trapping warm air, and I think that using two quilts on top of each other would cause too much air to escape. I use a 20 degree bag, liner, and base layer in the winter on top of a CCF pad and an inflatable pad. It works pretty well because I can keep the warm air inside the bag, although my shoulders get cold because it's a rectangular bag. A mummy bag may work better.
I'm 5'6", or 5'7" on a good day. It would probably be a tight for you. It is just the right size for me, not too big, not too small. See if there is a long version. This is the exact one I purchased: http://www.amazon.com/AEGISMAX-Outdoor-Urltra-Light-sleeping-Urltra-compactable/dp/B00XE2SKG2?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
> Aegismax Ultralight Sleeping Bag
Only 70$ US on Amazon if you're in US
I've been really happy with the performance of my Sea-to-Summit SparkII sleeping bag, very light at 16.4oz ~ 35F lower limit. Purchased mine from REI with a 25% discount during their membership deals earlier this year which would get you under the $300 price point.
Ultimately, it will come down to understanding the versatility you need and if you want a bag vs. quilt. Also, given that you are posting in /r/Ultralight, you will receive recommendations for bags and quilts pushing your $300 max, with the weight savings and warmth of 850-950 down fill.
As already mentioned, Enlightened Equipment is worth checking out. Also, Marmot and Mountain Hardwear both make some very nice, lightweight bags.
There are cheaper alternatives while still lightweight, such as AEGISMAX and Hyke & Byke, that can be purchased on Amazon or Alibaba. You can find some decent reviews and threads of those in this subreddit. Good luck!
AEGISMAX Outdoor Ultra-Light https://www.amazon.com/dp/B00XE2SKG2/ref=cm_sw_r_cp_api_glt_fabc_F76ATFFBW00VWXM3KQ69?psc=1
Get the aegismax down quilt/bag: https://www.amazon.com/AEGISMAX-Urltra-Light-Sleeping-Three-Season-L200cmW86cm/dp/B00XE2SKG2/ref=sr_1_26?keywords=down+quilt+camping&qid=1566150006&s=gateway&sr=8-26
You can use it as a quilt or a bag.
Sorry, this one
AEGISMAX Outdoor Urltra-Light Goose Down Sleeping Bag Three-Season Down Sleeping Bag Mummy Down Sleeping Bag Green L200cmW86cm https://www.amazon.com/dp/B00XE2SKG2/ref=cm_sw_r_cp_apa_sKCnAb0ZV0GQD
Google for reviews.
Aegismax sleeping bags would work for your temp range but they have to ship from China and may not reach you in time. I think my buddy got his within 2 weeks though.
Underground Quilts usually has rentals available but looks like they are out of top quilts at the moment. Not sure if that will change in the next 2 weeks or not.
Hammocks are great. Most people seem to choose them over ground simply for comfort. While it's definitely possible to get an UL hammock sleep system, they're less versatile especially considering areas without tree cover (deserts, hiking above the tree line, etc.) I recommend checking out /r/hammockcamping or hammockforums.net if you're interested in learning more.
Personally, I use a HG Cuben Fiber tarp, Dutch 11ft netless (w/ridgeline and whoopie slings) with a DIY half bugnet (HUG net), 30* HG Underquilt (just the 40* with 2 ounces more down), and the Aegismax green sleeping bag. I love this setup, and all together, it weighs 3.32lbs. Can I go lighter? Sure, but it's all a matter of preference.