Your choices are more then enough to play and see LFS in all its brilliance

My sytems:
PC1:
CPU: AMD Athlon 64, 3500+ (Venice S939)
HDD: Samsung Spinpoint, 250 GB (SATA-II)
HDD: Seagate Barracuda 160 MB (SATA NCQ)
GFX: NVIDIA GeForce 6800 GS
RAM: 1024 MB (2x Corsair VS512MB400)
Mobo: ASRock 939 Dual-SATA2
Monitor 17" BenQ FP71E
more then enough for LFS but I think I'll upgrade it this year

and it also runs on my 2nd PC without a problem.
PC2:
CPU: AMD Athlon XP 3200+ (Barton)
HDD: IBM Deskstar 120 GB (ULTRA-ATA 100)
HDD: Samsung Spinpoint 80 GB (Ultra-ATA 133)
HDD: Samsung Spinpoint 160 GB (SATA)
GFX: NVIDIA GeForce FX 5900
RAM: 1024MB (2x TakeMS PC3200)
Mobo: MSI KT6V-LSR
Monitor 19" IIYAMA Vision Master 451