I highly recommend looking for cheap-ass rackmount gear on eBay. I bought a jhs digital delay and roland reverb unit recently, both for £30-£40, and have got a ton of use from both. Rackmount gear is great because it stacks and I find it much easier to use in a studio setting.
The Waldorf 2-Pole is a great value bit of kit for the money too, I've been using this loads, the resonant hpf and drive are really useful with the Tempest.