Go for sub or larger speakers?

Marty,

You could pick up a used Theta Casablance III with 1 Xtreme card for about $4,000, and use it in a 2.1 application. I own a CBIII with XTreme card so I can give you some advice here. From what I gather you want to consolidate boxes, and need four things; Preamp, DAC, EQ and Xover. The CBIII will not give you EQ, so you still need yout SMS-1. The Xtreme card is a good (10 year old) DAC in a MCH application, but a modern 2 channel DAC beats it hands down (I have a PS Audio Perfect Wave which is a better DAC). Xover flexibility is second to none in the CBIII - no issues here. However, your LS25 is a far better preamp than the CBIII (I use a Theta Six Shooter for preamp, which is far better than the analog bypass in the CBIII). In summary, depending on what DAC you are currently using, you will very likely take a big sound quality hit with a CBIII, still have a two box solution, all for the questionable benefit of having a good Xover in a box 40lbs box (with I bunch of features you don't need).

A far more promising alternative is to look into the TACT 2.2 digital preamps with build in EQ and Xover. This has all the four functions you need in one box. I suspect the (optional) buld in DAC is the weakest link - but not to worry, it has digital out so you can hook it up to an External DAC. The only wildcard here is you are going from volume control with your LS25 tube preamp, to doing it in the digital domain. This would be anathema for purists, but since you are considering a CBIII and are not loosing any sleep over using a cheap Xover in an otherwise high grade system, obviously you are not a purist (I say this as a positive).

Edorr,

Thanks for the advice. I appreciate you taking the time to share your experience since it is precisely on point. I've thought about the TacT option and my main concern until now has been set-up complexity (I've seen a number of posts on various forums that have complained about that). However, that concern is now secondary to the volume control issue, mostly because it didn't occur to me that the volume control was in the digital domain until reading your post. One step forward, two steps back....

The likely result is that I will continue to delay any decision and enjoy the system as it is right now, which is extremely satisfyiong top listen to, if just slightly philosophically bothersome to the audiophile in me.

Thanks again,

Marty

I have some design experience with large full-range speakers and roughly comparable satellite/subwoofer systems, and imho done correctly the latter will have better bass quality and no audible integration anomalies.

Duke

Well, until a week ago I can absolutely say I was totally against using a sub with a full range loudspeaker. I have Avalon Eidolon Diamonds that I absolutely love. The bass is fast and tuneful.

I've heard these speakers in a similar sized room to mine but on a concrete slab floor. My room is an upstairs room with a wooden floor. In my room, with fast and tuneful bass, I have extension only down to around 35Hz. It's just the way the room is and interacts with my Eidolons.

A friend of mine works at a high end AV company in town and they were demoing a REL Gibraltor G1 sub. He suggested I try it out for kicks. Well needless to say my jaw dropped at what I was missing. The REL integrated perfectly with my Eidolons. The ass remained fast and tuneful but with extension down to 20Hz and basically a flat response from 20-40Hz, the sound as amazing.
I still remained perplexed on how changing my sound in the 20-40Hz range gives me tons more air, and widens the soundstage dramatically. Imaging seemed even more solid. And bass impact became a true visceral experience.

I highly recommend people with full range speakers not getting the bass they ant in their particular listening room to try out a sub. You may be surprised. And the way, the new G1 sub from REL is possibly their bet yet. I just ordered one.