There is no MC-505 VSTi or plugin, but the drums of it are avaible as samples (wav and exs24 format) on some sites.
And the synthesizer of it is like the calmer brother of the
TB-303, so you could just use the RB-388 or any
Roland-emulating software to make similar sounds.
The step-sequencer of it can easily be simulated with
Fruity Loops or with bigger quantizing in Cubase's Note-editor.
And the D-Beam Controller is a little similar to Korgs Chaos-pad which is quite cheap but very funky nonetheless. You just touch the pad instead of making wind. On stage it looks interesting as well.
Many Software-samplers are good, but I prefer Steinberg Halion.
If you're going to d/l it somewhere (what I would harshly convict), then you can just d/l them all instead and check sort out 1 by 1.
If you're looking for a Drumsampler, get Waldorf Attack or Native Instruments Battery.
The coolest Vocoders (or is it Vocodi?) I know are the Orange Vocoder and Fusion: Vocode from Opcode.
Oh, and if you don't have a mixer yet, get a Mackie.
It's the best for what your band-setup looks like.
Many channels, rough case (good for live-performance), best service in the world, exellent eq's (really, a mackie-trademark), enough out's & in's and Mackie-mixers have the most pressure of all.
Besides, Liam uses that gear as well. If that is of importance to you.