Your opinions on what speakers to go with?

I listen mostly to rock, dance/trance, female vocals?

My system is comprised of Rogue Audio M150 Monoblocks, Rogue Audio Perseus Preamp, Consonance Turandot Player, and Monitor RS8's speakers.

I am looking to upgrade the speakers and I would like to know your opinions on what to go with (or what companies make a system that for the most part sound great with the music that I listen to).

My problem is when I raise the volume only to mid levels I start hearing distortion coming from the Monitors, as well as sounds mixing together (when they shouldn't). I like to listen to my music loud so please keep that in mind.

Please any suggestions would be greatly appreciated.

You need to think about pro speakers - your current speakers are already quite powerful but you are having the typical compression and "ringing" issues from consumer designs (rigid light weight cones small VC's and small motors). You probably listen louder than most people and need an internally damped (doped fabric or paper/pup) traditional type design.

Check out ATC, PMC, Meyer, and JBL studio monitors and you will surely find something you like. Big horns such as large Tannoys or traditional corner loaded Klipsch's (old but they are famous for good reason) are also an option that will suit your taste for loud and dynamic sound (like the real live performance).

Be wary of typical low cost towers with multiple woofers - it looks impressive but the woofers soon compress - better a simple two way like Meyer X-10 with two expensive high performance pro drivers than a multitude of cheap low cost woofers. What you see is not always what you get. What looks impressive is often just that - looks.
I pretty much disagree with Shadorne. Nice system! I owned 150s. It should be in Ultralinear and you should be using KT 88s. Also I found tube bias needed to be adjusted regularly. You could have some dead (or near dead) tubes.

Power cords, interconnects, and speaker cables all make a difference. I really like Morrow Audio MAP2 power cords, Either PS Audio Transcendent silver interconnects or DH Labs Revelation. Get XLR if the preamp has XLR I/Os, if not replace it with a differentially balanced preamp! Ditto the Consonance. The Raysonic 165 is killer and the balanced tube outs are so good you can eliminate the preamp all together! Clear Day solid core silver shotgun speaker cables. If after doing this you still have speaker issues look at Usher, Triangle, Reference 3A...
Of course, if this is something you are only experiencing recently then Tweak could be quite correct - you may have a tube issue. Another challenge could be microphonics when you play loud. Pink Floyd's studio have their tubes in an entirely separate room to avoid the microphonic problems at higher volume levels. I seriously doubt if cables/interconnects can cure a problem that only appears at higher volumes.

My advice was based on your stated interest in trance/dance genre and "like to listen loud". Check out this setup from a guy who mixes for Kaskade and other DJ's for club music.
I had a pair of Monitor Audio silver s8's, which I believe were the british made predecessor of your RS8s. I recently dumped them off for a pair of Quad 22L2s. I can't honestly say I had any problems with distortion at moderate listening levels, but I have all solid state gear (Musical Fidelity A308 Integrated and a benchmark dac1).

The MAs have an abundance of low end base given the 3 6 1/2" drivers and dual rear ports. My complaint with them was boomy low frequency and shrill high frequency with the metallic dome tweeters at increased volume, so that may be the muddiness you're hearing (not really distortion, just poor imaging due to an overload of low end response). I agree though that power conditioning, better power cables and solid interconnects can clean up the sound quite a bit. You could probably get away with pure silver since you're using a tube setup (I found I can't as it's too much HF emphasis). I'll be the first to admit I'm not an expert (nor even close), but I've learned some through the growing pains of system upgrades and dealing with MAs.

The Quads throw out a much better sound stage and better the expense of low end frequency response of course (one less 6 1/2" driver and one less rear port).
I strongly suggest you check out Digital Phase AP-4's.
They are made to order for your requirements.
Would the Usher BE-718's do the job, or would I need to stick with CP-8871's?

Thanks for all of your posts...

One word: Bose.
your queston regarding Usher dancer series would require knowing your room size, the tiny dancer works very well in a small room whereas the larger dancer series realy requires a much larger room. Many of the Usher speakers will work well with lower power amps but the dancer series loves power. Your mono blocks would be a nice match with the 8871 and we have powered the tiny dancer and a pair of 8571 with a big rogue stereo amp with very good results.
Consider line arrays (Sealh Audio, GR Research among others).
Shadorne is right. Klipsch gives the best bang for the buck. Especially horns like the ones used in Quartets. I have used them with a 7270 McIntosh SS amp hooked to a C-1 Carver preamp, and now a Cary V12R tube amp and a Cary SLP98P preamp, and they sound great. The old SS system had 6 different sound processors that have now been eliminated, since I went to all tubes. Good luck.
I have revel f52 towers and rogue m150 monos with a bel canto dac 3 cd 2 transport and it sounds fantastic !!!
the rogues drive the hell out of the revels loud to me is in the low to mid 90-95 db, do you need louder than that?
some people do, just a sugestion and good luck, chris