crossover newb with passive subwoofer questions


I am considering purchasing a stand alone crossover for my system.
My system is comprised of the following, source to speakers:
MacMini to DAC to tube line preamp to tube amplifier to *passive* subwoofers (one per channel) with monitor satellites wired off their respective channel subwoofer.
The crossover devices that I've seen all seem to have RCA outputs (rather than speaker outs) which would imply to me that that the subwoofer and satellites would need their own amplifier.
Is there a device, or way to avoid the need for another amplifier,using a crossover "seperate" with my passive subwoofer/satellite setup? I'm assuming that such an animal would allow for wiring the speakers for each channel in more of a parallel arrangement, as opposed to a series arrangement as I have them now....
rabco
Frankly, if you use the Onkyo, you will still be faced with the problem that you lack proper crossovers. Y-connectors are a non-issue; use 'em if you need 'em.

Kal
Kal, understood.
All the input has been helpful!
Now I can start weighing the pros and cons, and plot my next move.
Just for giggles, as it's been years and many rig modifications ago since I listened to the Legacy's "naked", I think I'll listen to the monitors alone and re-evaluate their sound without the subs.
The results of this experiment might help justify the additional expense of a proper subwoofer.