I purchased some cheap $800 Dell with a ~22" 1080p DVI LCD from BestBuy back in 2008 Tax Season.
4850, i7-920(stock) 4gb1066(4 1gb peices, wtf Dell), and in 2009 Tax Season I purchase an Antec NEW TP750
For being a cheap f'n Dell, it actually is quite good. x58 chipset with an integrated Intel gig NIC. I can transfer 110MB/sec to my wife's comp over SMB and only use 1.5% cpu.
I purchase this computer as a "starter" computer, with which I would upgrade piece by piece until it was completely custom. My prior computer was an Athlon 2500+(single core 1.833ghz) 1GB ram and 5900FX that I built in college back in 2002.
For $800, it was impossible to build a custom comp to compete in price.
Next year I'm planning on one of those Ivy Bridge 22nm Intel chips and an SSD for my upgrades for 2012 Tax Season. My 1600 memory will work with the higher end triple channel Ivy Bridge chips
edit: I didn't want to bump anything so I edited, but thanks to everyone with their suggestions in other posts.