I am thinking of getting a Rane unless you want to make me a Crossver Altec? Please let me know?

The Rane will go between the Tube preamp and Tube amnp as I keep music and HT close by apart.

I'm using the dbx brand between my tube pre and power amps. They seem fine.

Generally, any crossover made for pro applications is not going to be up to the standards of the rest of your system. Rane, Samson, Behringer etc are all made for PA and other such uses, not audiophile grade. Cheap capacitors are the main culprit, followed by the overly-complex-for-what-you-need state variable filter implementation.

Check this link out - they make what you need.

Marchand Electronics

Marchand are way too costly!

Well, what can I say?!?!?!!!

If you've taken the time and money to invest in tube gear and upgrades, what sense does it make to place some dog-crap piece of gear in the signal chain which is going to mess up the otherwise good sound?

I don't understand the logic, but then again, I have a simple mind.......

Can you build me an active crossover?

Sure, but it would cost you about 3 times the cost of the Marchand ones I posted a link to.

My time isn't cheap.

This is confusing to me. According to reviews posted online, both your preamp and your amplifier cost over $2000. Yet, the most you want to spend on a crossover seems to be $500. Placing the crossover in the system will affect the sound of the system almost, if not, more than changing out the preamp or the amplifier. Think about it. You're asking the crossover to take in the signal, split the signal, and then output the signal to its destination. For the care and expense you've taken to put together the rest of your components, it seems odd not to take the same kind of care here. Just my .02 cents...

The Marchand Electronics crossovers that Altec recommended seem to fit the rest of your system perfectly with regards to budget and the level of everything else. There's always used.

If you haven't done electronics building before, an active crossover is probably not the best place to start, but ... if you don't get frustrated easily, if you can read, understand and follow directions, if you can carefully observe what you're doing, you might be able to go the 'kit' route - eventually.

If you're not experienced but tempted to try, I'd pick a couple other projects of a simple and less expensive nature to build first - see what you can learn, test your own abilities. They don't even have to be audio projects. (I'm talking about assembly here, not about circuit design.) I'm comfortable with such a project, but then I started watching my dad build Heathkit electronics and started with some simple projects a few decades ago.

If you're not going to venture into such a project, don't lament the cost of a Marchand or similar unit too much. When an electronics hobbiest is buying a limited number of high-quality parts, the hobbiest is paying more for the parts in the first place than a business that may use thousands of the same part. The Marchand units have a proven track record and carry a warranty.

I picked up a Behringer unit, used, for about half price to experiment with, not to use long term. If the concept works well with my speakers, showing an advantage over the standard passive crossovers, then I'll take the time and effort to make, or spend the money to buy, active crossovers on par with the rest of the gear. I'm not relying on my ears alone either. I bought a pair of test microphones and plan some 'before and after' measuring and analysis. After all, sounding different isn't automatically better, and very small differences don't always deserve the budget needed to go 'active' on the front three or all around.

EDIT: Pardon me, but I just re-read the initial post in this thread ...

If you're looking for an crossover for the subs/mains split only, via an external unit, you might find a used Outlaw ICBM. The ICBM can handle stereo subs too, but is a maximum of a 6.1 unit. For 7.1, the rear surrounds are run mono via the ICBM.

There are also used SMS-1 units if you're looking to 'tune' a sub's response to a particular environment. And don't forget room treatment(s) if they'll fit your environment - if the room is causing a major problem, it's often better to fix the room rather than relying on EQ alone.