It depends on what you are planning channel wise and lights wise, and what effects you are using.
The LED Flexstrips need pretty hefty processing to add the effects in the LSP sequencer, expecially some of the newer Macros
If you are shooting for say 3000 channels and above of LED Flexstrip/smart string then I'd advise to go for a higher end machine e.g.
i7 Quad Core, dedicated graphics, Win 7 64 bit and 8-16 Gig RAM
If it's say upto a 1000 channels LED Flexstrip/smart string then I'd advise to go for a Mid-range machine e.g.
i5 Dual core, dedicated graphics, Win 7 64 bit and 4-8 Gig RAM
If it doesn't have LED Flexstrip/smart string and it say a couple of hundred channels, then a lower end machine might surfice.