Ohm Walsh Micro Talls: who's actually heard 'em?

You are correct about the "in-line" set up. Go ahead with your plans. I would do some critical listening before and after the sub is in the system. Don't pay much attention to the bass, which will of course be different. Listen for changes in the upper bass, mids and treble. Listen for detail, soundstage dimensionality, timbre, etc. If you feel these are worse with the sub in the system, consider using the line outputs from the Nova. Make sure the output is variable level, so volume changes to the speakers will match volume changes to the sub. Note that, from what I see in the image, there is no internal x-over in the Nova, so that the Ohms will still get a full-range signal. This will eliminate some of the advantages of a powered sub - less amp power is required for the main speakers, which usually improves performance. Of course, you can always look into outboard, higher quality crossovers in the future.

How do i make sure the "output is variable level?" And until I can afford a second pair of good quality speaker cables I'm going to have to go with the preamp out on the Nova as opposed to in-line anyway. I appreciate all the help, I'm slowly coming to understand how all of this works!

It should be specified in the owner's manual. Sometimes, preamp outputs are fixed-level, like a tape-out output, so that the sugnal is at a constant setting. The variable level output will be affected by adjustments to the Nova's volume control. If you are not sure, connect the preamp output to the subwoofer, lower the subwoofer's volume to zero. Put on some music, then gradually increase the subwoofer's volume control. Once you can hear the subwoofer putting out a signal (audible bass), lower the Nova's volume slowly until it is at zero. If you still hear the subwoofer, but the main speakers are silent, you are connected to a fixed-level preamp output. If the subwoofer also goes silent, you have variable level. BTW, some preamps and amps allow you to select variable or fixed output via a switch or set up program.

Anyone seen or tried the sub that John @ Ohm offers? I do not believe it is an in house design, but seems pretty inexpensive at $250 in black and OHM will re-veneer to match existing walsh models

I'm also curious about the Ohm sub. Anyone know anything about it? A picture, even? It'd be half the price I paid for the Velodyne, so maybe I'd consider swapping.