Yes, what Ratboy says is true. The pre-amp colours and defines tone more than the post-amp because when a gain knob is cranked, it is the pre-gain that's being cranked, not the post-amp (which happens to be the volume knob).
And for sub's point above, I won't be able to tell (since I've only started playing guitar not too long ago), it would seem logical to say so. Reason being, as mentioned before in my earlier post here,
SS amps are great a reproducing hi-fi quality sounds. Manufacturers are no longer (I'm not sure if they ever did) getting overdrives from SS amps by allowing people to crank a SS pre-gain because it won't make much sense. Imgaine having hard-clipped tone as you crank your pre-gain on an SS amp... Ears will surely bleed.
What they are doing now (or have been since the start) is to get a emulating circuit or a "mini" pedal there. Pedals that come to mind would be Sansamp GT-2, or a MI audio TubeZone or even a simple Visual Sound Jekyll and Hyde. SS amps are (or were) employing variations these "in-built" circuits into their drive channels (eg jekyll as drive 1 and hyde as drive 2 or tweed as drive 1, brit as drive 2 and cali as drive 3). It is these emulating circuits which are improving, to give SS amps the ability to better reproduce tubeful tones. And how much do these circuits cost? Definately much cheaper than the price of these pedals being sold in stores... This, imo, gives low budget ss amps an edge of low budget tube amps.