Seems like you can
https://www.amazon.com/Lenovo-ThinkPad-20FB002LUS-UltraBook-2560x1440/dp/B01DHTXME6/ref=sr_1_4
You should do some research though to find out if thats the only model that supports it. I'd have thought upgrading it to 16Gb yourself would be the cheaper option if every model supported it.
What about this Lenovo X1 Carbon then ? comes with specs you want while still being light and very well built and thin as well.
You are not leaving us many option, no HP, no Asus, no Thinkpad X260, no Razor, What about this Lenovo X1 Carbon because it comes with everything you mentioned in your post "i7 preferably 512 ssd or more 16gb ram LONG battery life 7 hours or more small form factor"
I can think of couple of good options, the thinkpad x1 or this Dell Inspiron 13 both come with i7 dual core CPU which is one of the best in the market and great for your usage, 16 GB of ram for smooth multitasking, Good SSD storage of 512GB for faster boot up and loading, both around 3 lbs, both have decent battery life, and are within your budget.
Firefox? Man, haven't heard that mentioned in awhile. Get Chrome, son!
Anyways, the XPS 13 is a nice machine. It's pretty expensive for the specs, but the portability is high and it's a pretty laptop, especially with the borderless display.
You could get a little more portability, more spec options, and a better keyboard from the <strong>Lenovo ThinkPad X1 Carbon</strong>. You should also net better battery life getting rid of the 3200x1800 touch display in the XPS 13. More pixels = more battery drain. Touch displays contribute to that as well. In a realistic scenario, you should get over 7 hours of battery life from constant browsing on the X1 carbon, but only a bit over 5 with the XPS 13.
There is also the matter of the XPS 13 being a high quality consumer grade laptop and the X1 Carbon being a business class machine built for durability.
You can also configure your own <strong>here</strong>, but you will have to wait for them to configure and ship it.
I would highly suggest you throwing your music collection on Google drive or something, though. Free storage accessible anywhere is much nicer than relying on local storage, but I understand the appeal.
Your budget allows for a lot, though. The <strong>HP Spectre X360</strong> is a great machine if convertibles appealed to you at all for less, but you don't like touch displays.