Yes get a PC. But seriously, there are websites and chat groups that specialise in custom laptops. Most of those are horrendously expensive and have built in obsolescence. Your best bet would be to contact one of those forums and get in touch with laptop gurus/builders who might have a refurbished unit with a new hard drive, graphics card and battery. That is the only way I see you might get what you want at that sort of price.
I dont know if laptops support pci express for graphics cards, but whatever their equivalent is, is what you want. You may know 2.1 is the current standard but the prior version 1.?? will certainly do. A card with 1gb should be the minimum but 500gb would suffice. Main memory woud be crucial to its performance. Any 64 bit operating system will allow for usage of 3.2> + < mb of memory. (8gb would be perfect). 1333mhz FSB with a core 2 duo, (pref 3ghz) would be quite a capable system for SL. What else..... All I have to add is that the compnents I have mentioned are mostly considered three generations old now so you *should be able to get a bargain liasing with the right people.
In summary:
2.8 to 3.0 ghz Central Processing Unit, 64 bit Operating System, (old one-vista every1 hates it/cheap, even XP64 possibly), 8gb of RAM@1333Mhz, 1333Mhz front side bus. PCIE Graphics card 1gb memory, New Sata 2 hard drive, new battery. Print these out if you want and use the list to get quotes or estimates. This specification was my last PC and it ran superbly.