which monofonic?

[AnalogKid]

In my opinion, your best bet would be to dispense with the vintage synth idea and get yourself an entry level synthesizers.com modular synthesizer. Here are the reasons why:
1) The synthesizers.com modular system is real analog with fat sound (no matter how "realistic" the VAs may claim to be, it will kill the VAs). Not only is it real analog, but you won't have problems with tuning drift, which is a well known problem with vintage analog synths, even when they were brand new.
2) Not only will you learn how to use a modular synthesizer, but you can expand it as your budget allows. You can grow your two oscillator entry level system into a custom huge modular monster by adding modules of your choosing as your budget allows. Try doing that with a CS-15, Pro-One, etc.
3) Vintage synths are notoriously unreliable and expensive to fix when (it's only a matter of time) something goes wrong. They can cost and arm and leg to repair if you can find a tech who knows how to work on them and if parts can be found. Why buy an old and potentially unreliable synth when you can have a new analog synth with new components.
4) From what I've read, Synthesizers.com has great customer service. Try getting Yamaha to provide a new component for a CS-15.

Here's the link. When it opens, you can select the entry system to read about it:

http://www.synthesizers.com/systems.html

[Stab Frenzy]

A dotcom system would be an awesome choice, but it's not really within the budget of someone who can't even afford a second-hand rogue. I guess if you got the entry level system and built it a module at a time it could be affordable.

I personally went with a Eurorack system, more variety, can be cheaper or more expensive if you want, but mostly because a medium sized system is still giggable.

But yes, a modular is by its very nature as affordable as you want it to be. Of course once you start one you don't want it to be affordable any more.

[nathanscribe]

don't tell any of your lady friends that their holiday dresses make them look "rounded and solid."

Ye gods, no.