Yeah, I probably wouldn't sink any more money into it at this point. You could probably replace the fans without too much fuss, but with laptops at that age I always worry about what's going to go wrong next. That 4GB limitation is pretty harsh, too. As far as the SSD goes, you're probably limited to 3Gb/s SATA, so while it'll definitely be a nice boost you're not going to be able to see its full potential.
And honestly, I'd give up on the idea of getting a simple system for one big reason: cooling. I don't know why, but the concept of having proper cooling seems to have escaped many laptop manufacturers. Not sure if I posted specifics (and I'm too lazy to scroll up) but the laptop that I replaced with the ASUS had an i7 and a GT 650m sharing a single heat pipe and fan. Even laptops without discrete video get far hotter than they should because the thermal design is terrible.
Strange as it may sound, I would probably recommend getting a low-end gaming laptop. Look for a last-gen ASUS ROG (the one that I bought is clearly an older model, since it came with Windows 8 -- not 8.1 -- and uses a GeForce 7-series instead of an 8-series). Odds are it won't break the bank and it'll run nice and cool for you. Just to give you an idea of how it would compare to a "normal" laptop, I bought the last-gen ROG for the same price as an HP ENVY 17, which had less RAM, a slower CPU, onboard video, a single drive bay, and was widely reported to overheat on the good ol' Intertubes.
When I was looking to replace the Dell I explicitly did
not want a gaming laptop. I only bought one because it was amazingly cheap and perfectly matched my basic needs (decent processor, 8GB+ of RAM, 1080p screen).
Another option is to get a mid-range business machine, or an older high-end workstation. I saw a Dell Precision on Newegg (I think it was an M4600...it was using a Sandy Bridge i7) for $400. I use an M4800 at work and it's a fantastic laptop. LunarKeys is using a last-gen HP EliteBook (same class as the Precision), per my recommendation, and as far as I can tell he really likes it.
Another thing that I would look into is whether you'd want a single drive or a dual drive system. If you're taking an external HDD with you when you perform to store assets, it might be in your best interest to get a larger laptop with two drive bays, that way you can couple a fast SSD with a large HDD to get the best of both worlds (this is the approach that I like to take). If you're paranoid about data integrity and redundancy, you can pop two HDDs in and put them on a RAID 1 mirror, which will give you a bit of a speed boost over just one and prevent you from being SOL if one of your hard drives shits the bed. It gives you a bit more flexibility with the downside of basically requiring you to choose a 17" model. That would be pretty bulky compared to your U80a.
tl;dr LAPTOPS R KOOL