ATC 100 vs.150

My nephew has the active 100's- besides the woofer is there any reason to go with the 150's over the 100's = I do not want to get the 100's and wish I had gone with the 150's-my room is roughly 30' long- I also have the ATC c6 sub if that makes a difference- thanks,bill
Just the woofer/bigger box, Bill, - that is all.

The 100's and up all have the same bigger version of the midrange driver and are already a ton weight. So all you are really looking at is efficiency and a tiny bit more extension (a couple of decibels more and 6db point down further by about 5 Hz). Since you have the sub then my guess is that the extra bass extension is unlikely to be needed nor is the extra SPL for domestic listening (provided you use a preamp with bass management to allow the sub to do its job on stereo stuff). If you are against using a sub with two channel source material then you might consider the 150's a better choice.

FWIW. I have the 100's and the 0.1/15 sub in a similar sized room and it is deafening. With Sheffield Labs drum track CD (XRCD version) with Keltner (track 1) drum cresendos at 110 - 112 db SPL at a distant 10 - 12 feet back before beginning to sound anything other than effortless. I can't see anyone wanting more than this domestically and I have my setup tilted towards more bass and slightly rolled off highs (most pleasing in room response to me).

If you use them to watch movies or listen exclusively to classical then all this extra headroom (over normal speakers) becomes a significant feature. Otherwise I rarely push the speakers like on that demo track. Since movies and classical tend to have very low RMS sound levels with occasional bursts of huge dynamics - think Master & Commander Bu-ray opening scene then you can listen to movies/classical comfortably at much louder peak levels than modern hyper compressed pop/rock music. Dance club and good jazz recordings also make use of the dynamics and are mixed in a way that the music can be enjoyed loud (think Masekela, Hope, Stimela).

So your listening needs are a major part of the choice. If your nephew is a head banger and you only like soft music then you are talking overkill with the 100 and the 50 would be better.

I have not heard 150's against 100's in a shootout - although I have heard 150's and my impression was they sound just like 100's - probably because of the identical midrange driver/tweeter and the subtle differences in bass response being something that would require a careful shootout comparison in the same room to define.
If I have a pre that does not have bass mgmt- how do I incorporate the sub(C6) which does have a x-over into the mix-