FPS Drop when spawning NPC's.

[neurobuster]

So about two months ago, I replace my old 8400 GS with a newer XFX 250 GTS. Since then my performance in games have skyrocketed, and I'm very happy with my switch. But before I replaced my old card, I would always be able to spawn around 50 npc's without any significant lag. But now, whenever I try spawning around 10 npc's, my framerate drops dramatically. Like it goes from 60FPS down to 40FPS. I find this very strange, because other Source games, like Left 4 Dead, run fine with large amounts of enemies on screen.

I'd appreciate any info regarding this. And if it helps, here are my specs.
- XFX GeFore 250 GTS
- AMD Athlon X2 5000+ (2.6 GHz)
- 3 GB of Ram
- 575w LOGISYS PSU

[CombineGuru]

You have a logisys PSU.

[Danneh]

You got the latest drivers?

[neurobuster]

[QUOTE=djjkxbox;17815913]You got the latest drivers?[/QUOTE]

I believe I do. I have a feeling this has something more to do with my CPU than my GPU. As above user has said, maybe it's my PSU?

[Juggernog]

Your PSU is likely not powerful enough