The Poly 6 is VCO and sounds huge but still no midi. The Poly 800 came out right as midi came out and it responds to basic note info but only in omni mode. I learned this the hard way years ago when I bought two of them at the same time and could not figure out why I could not get them to play separate patterns. The Poly800mkII came out a bit later and had better midi implementation and swapped out the chorus for a digital delay.
The poly 800 can be had cheap but it doesn't have a warm full sound like a juno 106 or a huge vco sound like a poly 6. It is very thin and reedy sounding. Surgeon used it all over his early stuff, a lot of it was just a poly800 and a 909.
http://www.youtube.com/watch?v=DmCmW1EYuo0
http://www.youtube.com/watch?v=k1I5Vn1ECwA
I would love to post Badger Bite which was his signature Mill's rip-off anthem but it isn't on youtube. You will notice that he always used the gain on the mixer to over drive the poly 800. that was a cheap way of getting it to take more space in the mix because it was such a small sounding synth.
If you are looking for cheap hardware you might want to look into early Ensoniq stuff like the ESQ-1 or the SQ-80. The SQ-80 was Aril Brikha's main board during his classic period in the 90's. Groove La Chord is nothing but filter modulation routed to polyphonic aftertouch on an SQ-80 being fired by an MPC. They don't cost more than a few hundred dollars these days.
It doesn't really matter what you use, you just have to find a way to make it work for you. My next purchase is going to be whatever old digital synth I can find on Craiglist for a hundred bucks.