[Magnox]

Some nice stuff there. If you like that FM probabilities style of composing and fancied getting into hardware at some point, Elektron Digitone might be right up your street.
 

[Wanted: Used Roland SH-01A]

I have had a lot of synths come and go over the last few years. To buy new stuff, old stuff always has to go first. Regarding Roland boutiques I can only compare to what I have heard and spent time with but I used to own the Jupiter 8 and TB-03 Roland boutique devices. I sold both pretty quickly. The sound just does not compare in terms of quality to the cheap Behringer gear. I might pick up an SH-01 clone at some point. The Roland will not figure in my choice. It will be the Behringer or I may sell some eurorack pieces and get an Intellijel Atlantis.

[if you had to pick just ONE budget synth?]

I can totally concur on the Model:Cycles. You can write a complete tune with it. That's the downside of just getting a single synth like a Monologue (which is also a fantastic synth). I have to pack up all my gear in November and its getting shipped across the Atlantic home to the UK. The Cycles will definitely be coming in my luggage so I can have some gear while I'm in limbo.