SolidWorks just needs processor grunt and memory really. A faster outright processor speed is better for solidworks rather than something with loads of cores – the base modelling engine is a single-core only process at the moment.
Dedicated graphics cards helps, though you only need SW approved (Nvidia quadro and ati fire pro) cards if you want to use realview – i have that switched off most of the time anyway.
Dell’s outlet is great for this sort of thing, much reduced prices on their workstations…
To be honest, any of the 4800 or 6800 (or previous gen 4700 or 6700 if you’re lucky enough to find them) will cope more than happily. Get a decent screen res (Full HD at least) and you’re good to go.
The machine i’m typing on at the moment is a 6700 with i7 2.9GHz, 128Gb SSD (plus added extra 1Tb storage drive) FirePro m6000, with 16Gb RAM. It breezes SW stuff, which is what I use it for most of the time – I regularly work on large assemblies with great chunks of car body in them and it runs great. It cost 900 quid inc. vat from Dell Outlet…
http://outlet.euro.dell.com/Online/InventorySearch.aspx?brandid=6&c=uk&cs=ukdfb1&l=en&s=dfb
EDIT – stock gets update around 3pm Mon-Fri. You need to be on the ball, refreshing every minute or two around that time to get the bargains!