I still have a P5Q Premium as the main rig, with a Q9550 (changed with a Xeon E5450 for testing puposes and will be changed with a X5470 soon) and I'm actually happy with it. I have not much problem with games up to 2013-2014 (I always buy my games 4-5 years later when their prices are very low), but surfing thru bloated sites like facebook is problematic (probably due to still having 32bit OS and consequently utilizing just about 3.5 GB of 8GB RAM). At the moment I'm considering to add a SSD and go for multiboot with 64bit OS.
If you want high performance, playing recent games, etc., C2Q should not be your choice today, considering that core-i cpus get their nth (8 or 9?) generation update already (it was 2009 when I built this Q9550 rig). But if you want to make do with whatever on hand, and will be satisfied enough with mediocre performance (compared to contemporary rigs) like I do, I would say go with Xeon CPUs. They are cheaper than top LGA775 C2Q CPUs (Q9550 and up), but require some modding (both CPU and BIOS). This modifications are very simple though, and detailed information is already available online:
https://www.delidded.com/lga-771-to-775-adapter/ This site has very detailed and comprehensive information about the subject.
Please consider checking "Motherboard Compatibility" for your board though. supported CPU power for example might be a problem.
GA-6VTXE PIII 1.4+512MB
Geforce4 Ti 4200 64MB
Diamond Monster 3D 12MB SLI
SB AWE64 PNP+32MB
120GB IDE Samsung/80GB IDE Seagate/146GB SCSI Compaq/73GB SCSI IBM
Adaptec AHA29160
3com 3C905B-TX
Gotek+CF Reader
MSDOS 6.22+Win 3.11/95 OSR2.1/98SE/ME/2000