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....
None that I know of. Either you work at speaker level (where one set of amps drives all) or at preamp level (where a separate amp is needed for each output of the crossover).

I've been wondering if the benefit gained,a better integration of the subwoofers, which will come at the expense of complicating the signal path (introduction of a seperate amp for the subwoofers, the circuitry of the crossover,etc)will yield better sound, than simply leaving the setup as is.
I've spent a fair amount of time equalizing the bottom end thru the MacMini. I'm thinking the sonic footprint of the Mini might better be eliminated with a crossover and no equalization.
Not to mention freeing the Legacy Monitors (the satellites)from the influence of the subwoofers.
What you are currently using is a Speaker level crossover. Your amp feeds a full range signal to a crossover built into your sub. This crossover divides the signal sending part to your sub, and the rest to your other speakers.

What sub and speakers are you using? They may not be a good match with each other.
I'm using Cambridge Soundworks passive subwoofers with Legacy Monitors. The wires feeding the Legacy's are connected to the same posts on the subwoofers that accept the signal from the amp.
Then you are not using any crossover, at all, on the Legacy monitors and I don't know what those "subs" have as crossovers for themselves. I suspect none. Do you know?

Get a decent powered sub with a built-in amp and crossover.

This can be done with a capacitor feeding the monitors and an inductor on the subwoofer feed.Any idea of what frequency you would use for this crossover?
Do the "passive" subs have a level-control? And do you know the impedance of the sub and monitors?
I've assumed the passive subs have no crossover for themselves. I haven't gone to the length of contacting the manufacturer at this point.
As always, I'm trying to proceed to get the most for my audio dollar. I'm assuming a nice self powered sub could set me back, well, more than a good used crossover.
I could press a nice Onkyo ss amp into service to power the subs.
Opinions regarding the benefit I might realize by buying a used crossover & employing a seperate amp, vs the addition of several active devices are welcome.
If anyone cares to share their experience doing this, I'm all ears.
Tpsonic, no my equalizer isn't fine enough for me to hazard a guess about what frequency should be used for a crossover point. The passive subs have no level control. When discussing the impedance of the speakers with the manufacturer of my amp, he felt that setting the amp up for a 4 ohm load would be best. I know, a guestimate at best, for gear that's been matched piece meal without any formal measurement. I've been using it this way for years, but thought I might try this process as an upgrade.
First, you need a real crossover for both the main speakers and the sub. Second, you need a level control for the sub. Third, you need something to power the sub.

It appears that you are very "price sensitive" so I must tell you that I know of no mainstream affordable products that will suit your needs, new or used.

What will work and is inexpensive is a plate amp from sources like:

I've used the Parts-Express plate-amps and they are a reasonably priced fix.They are mono units.Since you are using two subs-two are required.
Onkyo for subs:You will need a crossover.Maybe a Dahlquist LP-1 or the NHT X-1.The LP-1 is passive (capacitor) on top and active on the bottom.If you have two outputs on your pre,you might run the monitors full-range and use the LP-1s' bottom (variable freq/gain) to control/balance the subs.This will allow you to adjust the subs and not introduce more circuitry into the monitors.
Kal, if I had my way, I'd be part of a 3 Corvette household, but the reality is.....reality! I manage to get unsolicited compliments on my system as it stands, and I steadily try to improve it over time.
Thanks for the links. I'll check them out.
Tpsonic, thanks for the suggestions.
My preamp is a simple tube line preamp with only one output. I suppose "Y'ing" the output with RCA lines, to what would be two separate amps would be a no-no for several different reasons....

Have you looked at these products at all? Many provide for an RCA input, a high-passed RCA output for the main channel speaker amp and, of course, internal routing to the subwoofer of the low-passed signals. No Y-connector is needed.

Kal, just covering all my bases with questions that address all my potential solutions.
For example, if I use my ss Onkyo as a subwoofer amp, I may need 2 pre outputs to drive the subwoofer amp and the tube amp that would drive the Legacy monitors.
I understood that some of the units in the links you provided are as you describe. Which may make them the most attractive way to proceed.
Just trying to sweat the details. These are devices I've only seen pictures of, & I haven't deployed.
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, understood.
All the input has been helpful!
Now I can start weighing the pros and cons, and plot my next move.
Easiest, but more expensive, solution is to buy a proper subwoofer.

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.