I think that lcrim is right on many counts here - the stock unit is very good, with clean highs, and amazing woofer control. A modded unit is even further down both sides of that road, without etching the highs, or woolying the lows.
Now, I can see why someone might want to use this as a bass amp, especially at the price. Money aside, this is still a very good platform, and with mods it is proving astoundingly good.
Like lcrim, the modded Teac that I have (a Bolder unit) has me with new speakers. I built up a set of CSS 4.5 inch full rangers, and I am shocked at how good they are, paired with this little amp.
I do not yet feel that each new piece of my system has settled down enough to offer a review, or report, but I will go on record saying that so far, this synergistic match is great - modded Teac, with CSS full range speakers.
I also have a stock Teac with VinnieR mods to just the power supply, that I am using as my surround amp, for HT. I will, once all break in, do a comparison of the following.
1 - stock Teac, stock PS
2 - stock Teac, VinnieR modded PS
3 - Bolder Teac
But back to the question at hand - do I think that a Teac amp would do well driving 100db bass drivers? Good lord yes, since you would really only ever use the first 1-5wpc, you should have a great match there - I do agree with lcrim that the Teac is capable of much more, but if this is your intent for your system, I would hazard a guess that you will be well rewarded. I would suggest trying the Teac full range at some point, following some of the simple DIY tricks so generously shared in this thread by others, to see if it floats your boat.
Back to the break in!