this is the second preamplifier gain thread that has popped up in recent days...
it seems to me that preamplifier gain is generally irrelevant: what i would think should matter to you is what is the input sensitivity of the preamplifier, what is the maximum output level from the the preamplifier and what the clipping voltage is for your power amplifier. if your sources provide signal levels (typically around 500mv) to the preamplifier that hit the input sensitivity level then you can hit the maximum output level at the output of the preamplifier. in all likelihood, that maximum output level from the preamplifier is more than enough to drive your power amplifier into clipping (which i think might typically occur at around 4v or 5v).
the other topic that i have frequently seen commented concerns impedance matching between the preamplifier and power amplifier. as a practical matter, i don't know how much that really is an issue. the preamplifier specifications should tell you what input impedance it needs to see to drive maximum voltage and that should be way below the input impedance of most power amplifiers. for example, i have a bryston bp-20 preamplifier - according to the specifications, it can drive a maximum voltage (15v) into impedance loads as low as 600 ohms. my power amplifier (a bryston 4b-st) has an input impedance of around 50kohm, so you can see that impedance matching isn't really an issue in my case.
in any event, you can check the specifications on this stuff to be sure in your case but hopefully you have a better idea of what kinds of data to check.
there is the whole area of passive preamplifiers but i don't know anything about that kind of equipment so there may be a different set of considerations for which to account.