Look at the top systems on the PPBM site to see what ones perform the best.
It is best if you build a system as compared to buying a system from a vendor like Dell.
I got a cheap system to hold me over till I build my system but my score is in the middle at 60.9 on the PPBM scale.
I got a Best Buy special.
Its nothing special but it runs OK.
It does NOT have a CUDA approved card but this isnt the machine I want to edit on anyway so I can go without MPE for now.
For SD video this unit is just fine.
For HDV its OK too but with AVCHD I would go with a bigger system.
Just look at the PPBM chart to see what builds do better to get a feel for what works.
I got a system custom built by a person who volunteers his expertise and experience to these forums (I found him online before I found the forums) namely, Scott Chichelli of ADK Editing out of Kentucky. Prior to the actual purchase he answered every question I had and we reconfigured the system half a dozen times to get it just right. The result...
i7 980x CPU
GTX 285 GPU
1TB hard drive for OS
2TB RAID 0 SOURCE/SCRATCH
2TB RAID 0 RENDER
ASUS 25.5 1920 X 1080 monitor
Windows 7 Pro 64
CS5 Production Premium
I've had it about six weeks and not one problem.
Handles HDV and the just released Canon XF300 & XF305 .MXF files without a hitch.
That is a nice system, but your perception of a decent price / budget may differ from the OP.
Some people consider $ 1.5K decent, others think $ 4 K decent and others consider $ 10+ K decent.