Well I am a guitar player and Keyboardplayer and I also use for composing some synth's.

Since you are not interested in autoaccomp.,
and you want a lot of filters etc...we can rule out all arrangers;

This is what I use to my satisfaction and which combination offers me all past sounds, todays sounds and future sounds;

1. Kurzweil K 2600 S + all daughterboards installed.
2. Virus C (rack controlled by the Kurz)

The ownly comment I can make, that The kurzweil will probably take the rest of my life to completely find all the possibilities.
This is a synth with a very high learning curve, which is also the reason that most button pushers don't like it.
Allthough it is now 5 years on the market, Soundwise/quality it is still a top synth.
(Not sure about future service if needed, as the mothercompany Young Chang filed chapter 11.)

Some other suggestions;

Easy to operate specially if you are new to synth's / workstations and offering high quality;

Yamaha Motif series

Roland Phantom series

Korg triton

If I had to make a choice out of above three I probably would go for the newest Roland, as I do have more Roland boards which have proven to be very reliable,(I use those on stage)

Hope this helps.

Fred