I've looked heavily in to the MS20 mini but it really seems a bit too far out my price range, I have a midi keyboard but i'm looking for something different, this was really just a cheap fill-in to start out with and i'm selling that as well as a few other bits and bobs to save up a bit of money. Definitely something brown townogue is what i'm looking for and the ms20 mini is something i'm going to work towards maybe next year, starting a college here in the uk for electronic music later this year and a lot of my savings are being spent towards moving house near the location of the college so i'm going to say £300 is really my absolute limit with what i can spend on something until next year so i'd like something until then to experiment with and also learn more about different oscillators/waves and such
edit: £300 is about $500
roland jp8000 (very nice yes)
arturia minibrute (very cheap yes)
polivoks (its all in russian and may use a strange power protocol though idk)
roland juno 106 (classic)
yamaha dx 7 (digital synthesis though, massive pussies use this)
xoxbox (or a tb 3 when they come out, both good for bass/acid)
or since you already have a keyboard you could look at the wide variety of synths with poorly done keyboards and MIDI outs, so you can use the keyboard you already have instead of the touchpad one or whatever it is like:
korg volcakeys
korg volcabass
and if you found a way to convert cv signals to midi you could buy many more synths that would be reaaaaaalllyy cheap (im talking 20 dollar cheap), but they aren't as versatile as the one's i first listed
good luck buddy