mmm first I want to state that the Doepfer is f*ckin awesome, and anybody not getting a good sound out of it should try harder, or look at the machine in a different way. This is a deep synth and there are no presets. Having said that go for the deluxe PSU. It will make it soundquality overall much better.
Ok the moog is a moog. period. you want that fat moog sound, go for it. Also consider getting a macbeth. These synths (also handmade) sound just as fat, controls are a bit different. IMHO
The moog is a players instrument. You'll enjoy playing it. Also has blingbling.
The doepfer is a different beast. It is a modular synth. You'll be able (when you're hooked) to change its configuration with many different modules. Not only doepfer's but other european manufacturer's as well. This is a highly programmable synth. You will enjoy programming it, as there is no substitute for real knobs and cables. The sound is... just as good as your programming skills. It can be very warm, clear as glass, nicely behaved, or vicious. The overall sound of some english and french modules is IMO a little bit more fuzzy and less direct. So if you want that get one or two different modules. Or insert a guitar pedal, or a tube compressor, or anything Quality is (go for the transformer PSU one) undisputable. also you need a midi-CV interface. For sequencerthings and clock you'll need that to use your computer. Has blingbling but in a weird way.
The Nord is amazing. It can be programmed just as the doepfer. And played like another small portable synth. There are two buts. 1. the nord will sound like a nord. This is not at all a bad thing. 2. in programming it, I noticed that you will get results when using a larger number of modules. when programming the doepfer the sound you are after is often achieved with only a few modules. This is IMO a significant difference, because the level of complexity rises with each selection of modules that you will have to use extra, making it more difficult to "grasp" the sound. I o w the doepfer is more complex than at first sight, the nord has a more easy way of adding and using a lot of steps in making a sound. Both are awesome machines. Simular in theory but different in their "way of doing it". Less blingbling for the G2.
Consider an Andromeda. It has been on my "need to get list" for sometime. Very complex. And a real Buchla. Blingbling plenty.
Rob a bank, and buy a Technosaurus or a sunsyn.
Ok which one? Don't go for two at the same time, because you have to learn one first. All of these synths (the moog too of course) have to be programmed. You'll have to know how substractive synths really work and how the individual building blocks sound. But you probably figured that out. Then get more synths, and enjoy the differences. The doepfer is a lifetime project. You can keep on buying modules. (I am its eternal slave). You'll find a lot of new patches all the time, if you try hard enough. (so maybe it a symbiosis) My (musician) friends have moogs, macbeths, nords and doepfers. I like all of my friend's synths, but the doepfer is addictive. I have a doepfer, and some arp axxes hooked on. (and some not-modular synths) Auditioning in shops is difficult, as the sounds depend on the quality of the programmer. So try to get some examples from regular users, or from the net.
If you want simplicity but good results, don't get a doepfer, or any of above. Screw it and go for a different concept like a rompler. or a nordlead, or consider a virus. (!) very fat both.
If you choose any of the above more programmable ones go for the deep end. You'll like it.
hope this is of any use (half past 3 am over here)
*this is someone else's doepfer*
http://www.synthfool.com/images/doepfer2.jpg
you could go for a cheaper software version. But there is nothing like hardware.
And this is gearslutz