Don't wanna be mean Keres, but that's like a 6 year old PC or something? I would not expect it to give fair fps at all.
By the way, 128MB agp doesn't mean anything. A 32MB PCI-card can be like 10 times faster. Same with Ghz's btw, they don't mean much, different between Pentium 3 1,4Ghz and Sempron2500 is huge, even though they're both 1400Mhz. And to some extent, the same goes for RAM. Depending on type/brand, the differences can be huge. So when giving specs, it's nice to be more specific.
And indeed it's not insane quality, but it's an old engine which isn't optimised at all for todays games/systems. So yeah, you will need a more beefy system than one might expect from the quality. The engine is not the only responsable for performance, it's what you do with the engine.
And of course the vis-blocking is missing on uptown, making it worse for you