Hi Frank. I too remembered the 2150's as having excellent bottom end "way back when". The first time i heard the amp, the first words out of the owner of the shop's mouth were "listen to the bottom end on this baby", etc... After comparing a few 2150's to a couple of 3150's in a side by side, there is NO comparison when it comes to bottom end impact and slam.
As far as the 1150 goes, i think that it sounded a little smoother than the 2150 but was a little lacking in terms of dynamic punch. This was probably due to the reduced amount of available power.
In terms of the availability of output devices, these amps use the same outputs as MANY amps i.e. B&K's, Muse, etc... to name a few. While there are some substitutes available, i don't know how well that they work. I have heard of some "heavy duty" versions that are basically a "double stamping" ( twice the amount of junctions within one casing), but i don't know much of a "drop-in" they would be. It should make for a very rugged device but as far as sonics go, who knows ???
As far as sticking with "reputable brands" i.e. long term servicability, i agree with what you are saying but also know that a manufacturer has no control over what is / isn't available on the market place. Don't you think that every manufacturer would like to produce a product that they could stand behind "forever" in terms of reputation ?
I know of a major manufacturer that built a product based around a specific Integrated Circuit, sold thousands of that product and when it came time to re-order, the manufacturer of that IC stated that it was no longer available and there was no substitute. What does a single manufacturer do in such a situation ???
While you would think that Hitachi, Toshiba, Motorola, Sanken, etc... would recognize the captive market that they have for some of these "unavailable" products and do a small production run every now and then, i guess that they have got bigger fish to fry. It's a shame too, as a lot of good products end up in the boneyard simply because we can't get the parts for them. Sean