Is there a pre-amp not processor with a sub out?

I've had good luck with running RCA interconnects directly to the sub. Then, using the other pre-amp RCA connection or XLR out to the power amp(s). That avoids the need to run interconnects from the sub to the amp or back to the preamp. The full bandwidth goes to both the sub (which is designed to handle it) and the power amp. You avoid a cross-over so get a cleaner signal to the amp. Virtually all class A preamps would allow that configuration.
A second suggestion is to utilize an outboard cross-over (lots of companies build these -- like Bryston -- or a great DIY project). One interconnect to the outboard and then two or three outputs -- low to sub, higher to amp(s).
The first suggestion is less expensive and, unless your ears tell you otherwise, could do the job. Good luck.

If you keep your mains out of the crossover then you only have to use a pair Y cables to send one pair of interconnects to the sub and the other to your amp. And the mains will sound much more pure without them going through the crossover.

Greg,
Here's a solution that I used and since you need a pre-amp, it would work for you and is pretty clean.
I used the EVS Ultimate Attenuators as a passive pre-amp. ($250 new - around $100-150 used depending on age and condition) I don't know of another product with a shorter, cleaner signal path. (I have no interest in them and none to sell either...just trying to give good info)
Connect the EVS directly into the back of an active x-over. (I used the Paradigm 30) 1 pair (use 1m or shorter here) of i/c's from your CD to the EVS. And from the x-o, run 1 pair of i/c's to the main amp (it goes through the high-pass on the x-o and there are positives from this) and then 1 i/c to the sub (assuming only 1 sub, you can use 2 subs with the P-30).
I got more detail and resolution with this set-up than through any active pre that I tried.
The x-o also acts as a buffer and from there, you can use longer i/c's to both the main amp and sub, if needed. I'm pretty sure I'm correct on that last comment. Anyone please correct me if I'm wrong or confirm if right?
Good luck

If a pre/pro is off limits, then look for a preamp that has two sets of main outs. Some will have 1 pair of XLR and another RCA.

I'm using a Primare P30 pre/pro and it is sonically superior to some 2-channel preamps in direct a/b comparisons in my home. One of which is highly rated as a class a preamp in Stereophile (not that that means anything).

Nevertheless, I'm using the RCA main outs for the sub and the XLR for the amp.

You could use Y-connectors but you always take the risk of degrading the signal.