Well, guys, it looks like more modern CPUs and RAM are already cheaper than what I have, plus, to be honest, I hate my mobo because of the frequent inexplicable losses of CMOS memory (but somehow connected with shutting off power), nor do I trust my PSU, so I guess this looks like a new computer should be underway.
I could theoretically keep my chassis, graphics, music, HDD, even DVD drive, even the PSU, at least for the time being, to save on the expenses, which would mean buying a mobo + CPU + RAM + Windows. But that would mean making the current computer basically unusable, whereas I'd prefer to keep it operational.
So I guess the optimal choice is a new PC after all. I could try overclocking but the problem here is that the mobo can't keep CMOS settings for whatever reason (battery is good), so putting back the overclock tends to be a pain. Nor do I really have the time, patience and attention span to test carefully all the small increments of FSB/CPU frequencies. Also had some stability/artifact problems, even without overclocking (on this GTX460 and the previous ATI 4850, so perhaps it was the PSU having a single 12V rail). I guess I'll have to try my hand at overclocking again (I do have an aftermarket cooler, Aerocool GT-1000, but I don't think it's oh so great).