I don't have much experience with amplifiers, but I must add: I have the SAZ-100.4 and four SAZ-1500Ds from Sundown and they're friggin' awesome.
i don't put much emphasis on "sq" of amps. for me i try to buy the most power i can afford with the necessary features i need out of an amp and also consider aesthetics.
I wouldn't concentrate so much on the "sq" aspect. Rather on the power output for your money, features in relation to what you need, the quality of the build as well as aesthetics and customer support.
If the amp fits into your price range, has the features you need and adequate power output; go for it.
If I were in the market for that price-level of amplifier, I wouldn't have any reservations about handing my money over to and supporting Sundown. Seems to be a great guy building a great product with the enthusiast in mind rather than pure profit margin. That is the type of company and person I like to support.
I like the Kicker ZX650.4 myself.
thts what im running though, and they can be had for cheap
I know nothing about amps and am just going on this board for recomendations. I probably will go with either this ,an eclipse,audison(local dealer will be doing install) or us amp. The audison has 65 x 2 and I dont really think there is much differance fromm 65 watts to 100. They said they will install anything I bring them but it might be better to buy from them. Whatever speakers I choose will deffinately not be from them tho,if i at least buy an amp from them I might get a little better service which will benifit me and the dealer. They also have an orion but i think my other choices are better quality.
what difference in THD can a nomal person detect.....not asking what the lowest THD that a person can detect distortion in but the smallest difference in two THD ratings. For example if one amp is x THD and the other is y THD what would be the neccesary difference in the two for someone to be able to notice a difference?
The differences in THD in most any solid state amplifier don't matter as they are still both below the audible threadshold (like they almost always will be with amplifiers).
For example; You'll never hear the difference between .000001% and 1%, and that's a pretty large difference.
It's not the "difference" that really matters, it's where the difference occurs. If they are both under 2%......it doesn't really matter how large the difference is.
how do you know? you are too lazy to put it in! lol