You'll probably get between 15-50 fps with R2. Spec and HTL models may cause massive drops. I'd suggest switching to non HTL models too if it's anything like my system:
Desktop:
AMD Athlon XP 3000+ @2.17GHz
ATI Radeon 9200SE AGP 256mb
1 GB DDR RAM
Runs slow in some areas, doesn't like HTL models
laptop:
Intel Pentium M 730 @1.6GHz
ATI Mobility Radeon X700 PCI-E 64MB dedicated
512MB DDR2 RAM
Runs at max with HTL models
R2 is far more demanding than R1 as it's bigger, with higher res textures. We've optimised everything the best we can (less textures per model, no tgas, both htl and non htl models, eff instead of ani files, dds maps) but it's still quite a beast. However I've tried to make sure it'll be playable on my desktop system so you should be fine, though you may have to sacrifice the HTL stuff.