Should I buy an MM6 or an S500 ???

Hey !

I am planning to buy a new keyboard and I am extremely confused on what to buy. I am familiar with using Yamaha keyboards like the PSR450, but I was not completely satisfied with what it had to offer. Right now I am considering to buy a Yamaha PSR S500 or a synthesizer. I have tried out a PSR S500 but it wasnt as great as i expected it to be, however it comes at such an affordable price!

-I want a keyboard which i can carry around for gigs as well as play at home, with a provision to connect to my computer to save my music and maybe download new voices off the net if thats possible.
-I play mostly rock, metal and gothic music (I like making trance music too :) ).
-I am very particular about the sound of the keyboard.
-It must have rich piano, strings, chorus voices, voice pads and a few electronic stuff.
-Must also provide effects like dual voice, sustain (without a pedal) and reverb, flanger, echo, etc
-Atleast have 5 octaves, with keys that dont feel too soft
-Should have one touch settings
-It would be nice if it looks cool too :)
-MOST IMPORTANTLY- It should cost me less than $1000 (I guess im asking a lot)

Ive never used a synth before...but they seem to have what Im lookin for.
So would you suggest I buy me a synth (like a Roland Juno D/ Korg X50/ Yamaha MM6/ Alesis Fusion 6HD/ etc....) or a Yamaha S500???

Thanks

Nigel