If you already have 10 GB, I think I'd try the other options first. Our machines have pretty slow memory by today's standards, but benchmarks do show slightly better performance if all slots are occupied. I just upped my system from 10 GB (4 x 2 GB in one bay and 2 x 1 GB (original memory) and 2 blank slots in other bay) to 12 GB by adding two more 1 GB sticks. Didn't run any benchmarks to see if it helped, but it was reasonably cheap.
You'll see the most speed improvement with the SSD and the 5770. (The 5870, by the way, doesn't speed things up enough more to justify the higher cost and higher power consumption.)
Much of my guidance is obtained from:
http://www.barefeats.com
Cheers,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB