I nearly posted something the other week about being confused about Modular mixers, there really isn't one that is suitable to fit all tastes.
Things like:
Lacks enough standard Stereo channels.
The add-on mixers lack Mutes and Pan control.
Takes up too much HP.
Its massively cheaper on Ebay, buy a Mackie, Behringer or Yamaha outboard mixer second hand or even new they can be a good price.
I've pretty much decided for the playing about I do with modular I'm better with small sub-mixers.
There is almost an argument for buying a few Befaco Out v3's as leveled Outs to a desktop Mixer.
I emailed a suggestion to Befaco a bit back, make an STMIX that has Stereo Mutes and Pan control attached, thats what I need/want, and it would make the STMIX a better more functional part when coupled with the Hexmix, and in turn the Hexmix more appealing with its mono panned and EQ'd channels with Stereo effects returns.
My Current mixers are; Befaco STMIX, 2x Doepfer A-138s (for percussion mixing), and a Happy Nerding 4xMix.
There are so many modules that are Stereo, I think I have 6 stereo-capable modules in my rack now and add the outputs of the 2x A-138s's and thats 8x Stereo outs I need before thinking about Mono.
I'll leave this here, in its vaguely confused state :)
Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.