I am not sure about the Scarlett 2i4 and how you would achieve what you want. Not really familiar with that sector of the industry.
Laptop wise, I know this may not be the norm for this site, but have you considered something like a Macbook Air 13? https/www.amazon.com/Apple-MMGF2LL-MacBook-13-3-Inch-VERSION/dp/B01EIUOSRS/ref=sr_1_3?ie=UTF8&qid=1469087170&sr=8-3&keywords=macbook+air+13
It's $925. The reason I recommend it is that Macs are very good at making music with its software and it is very light, fast (Core i5 2.7GHZ), with 8GB RAM and a 128GB M.2 SSD. The screen isn't that great (1440x900) but apart from that its amazing for the money. Remember, you could install Windows on it by using BootCamp. I'm personally not a huge fan of the Mac OS, but its been a long time since I've used it, and I am not familiar with it really.
If you want a native windows option, a traditional "bang for buck" laptop, then go for this one. https/www.amazon.com/ASUS-UX305-13-Inch-Laptop-model/dp/B01578SQFU/ref=sr_1_4?ie=UTF8&qid=1469087378&sr=8-4&keywords=asus+ux305
It's amazing for the money, has a Core M (not the best but still very good), 8GB RAM, double the storage of the Macbook, a slightly better 1080p screen, not to mention its incredibly light, thin. There's also a quad HD touchscreen version which is actually $2 cheaper, so you may want to go with that.
Hope this helps,