Never had problems with business spec Dells. I run everything on them - my corporate build on a D620 dual core, and most of my pen test stuff on D600s. They are all pretty fast, whether under XP (spit) or various Linuxes. They never crash (unless I make silly config mistakes) and they cope with pretty much anything I plug in. And their support is so good I bought my latest home server / games machine / vm box from them. Veyr good experience for me:-)

(of course ymmv)