I have 3 Bose T4s (one for my ceremony), one for my main DJ rig, and one for backup/and use with other systems or for far away fill speakers (I use the delay and high pass feature in that case).
I don't own the L1 Model 1 or Model II anymore so, yes, you need to buy the power supply.
It's a fanatic sounding quality mixer with full dsp, and scenes can be saved. Having the parametric eq makes eqing mics super easy and I can dial almost all feedback with an omnidirectional mic for my ceremonies. Having a noise gate helps too. I think I get more compliments from vendors, guests, and officiants on my ceremony sound than anything else, lol.
The way I use it for my main system go as follows:
Inputs 1 for MY personal mic, input 2 for the wireless mic, input 3/4 (stereo) from Pioneer DDJ controller. I then also use the USB for digital out from my computer when playing dinner music via iTunes/MegSeg (you can route the USB to any channel, even if you are already using the channel for something else).
It also makes one of the best options for live streaming which a lot of people are doing now as it is fully digital with the USB connection.
It has lots of generic presets such as 50 Herz, 80 hertz, etc high pass, and low pass, PEQ, global EQ, multiple aux outputs that can be processed individually, which is a huge plus. I can send a totally different signal to aux 1 or even a different signal to aux 2 from the master output.
Once you get it all dialed in, you don't mess with it too much. I just finese the eq per location. It's probably the fastest, most efficient, smallest, portable mixer with that much control that I know of. The QSC touchmix is much much bigger and mor $$. I also own a Xair 12, which is the closet thing I have to compare, but I almost never use it when I can dial in sound a lot more efficiently with the T4s, and it does not sound as good.
The T8s has more inputs...
If you have any questions, let me know. I know the ins and outs of the mixer quite well.
This was probably true in 2004. However, Many bands discovered they work great for bands. I use the Ts4 as it provides me with enough inputs. If I was a band and needed more inputs, I could use a t8s that provides more inputs