Any advise to improve my system

Well, Before you start changing all the variables around and switching gear, I'd say this...You've got some really good pieces to work with, so I'd work on getting the maximum out of what you've got first! And, if you must change gear, only do one piece at a time!!!..that way you know where your at with your system!
My first inclination in regards to your concern about bass muddle would be that your speaker placement in the room needs work! (Or your seating placement, or both.) Speaker placement and seating in a room are the most important in getting good bass response from the speakers!!! Most people don't even have a clue!..really!
If you have a small room, this is even more likely a challenge! You've got a much better chance of getting good/flat bass response if your in a large room to begin with...small rooms are much more work generally, and are more picky to speakers as well. Bass Traps in the corner are usually mandatory in helping get boom out of the room as well!
Also, with the detail, you migh want to consider acoustic room treatment considerations (i.e, diffusing/absorbing first reflection points). If you can't control (caution, balance here!) first wall reflection points, the detail is all smeared and non defined sounding!
Now, once you've worked your room/set-up where you've got the best your going to get out of it in your room, I'd say it's time to, yes ,upgrade those otherwise good for the $ speakers (not Stratus Gold I's either!!!..the silvers are better overall actually!) for more refined/detailed one's. There's a gillion clear/detailed/pretty speakers out there that, set-up correctly, will satisfy all YOUR music needs, and give you plenty of good bass!...from what music you said you favor that is! If your after tight fisted Rock and Roll speakers, that's another story entirely!...
When you finally get into other gear mode however, I'd start with this order of changing things from where you are now...speakers first, then, if amp/preamp works fine with your new speakers, then keep em. Otherwise, find some new pieces that work better with your new speakers. Then, experiment around with changing some (one at a time) cables to match your new system! If you must upgrade your CD player, that really can be done without any real problem. Good luck

The MIT cables are the weakest link in your system though I don't believe they would create the problems you mention....if anything bass should be their strong point. A cable change may be worth a try anyway. Your speakers are more likely the problem. Though they are very highly regarded, I have never found PSB speakers to have clean bass. Good extension, just not clean / tight. I'd audition some others and see what you like....I can't make a recommendation because I haven't heard Plinius. Good Luck, Dave

My experiences are the same as above. Your equipment should be enough to get you there. Speaker placement, isolation, shelving, tweeks... Search "winter lessons", those are my experiences that brought out the final 15%. And have fun! J.D.

Patrick, I'll take a shot. Here's what I'd do starting with the least expensive. Try a mit 2 power cord on your amp, the SR master on my classe makes the soundstage thick, slow and creates a mid bass hump that is distracting. Classe amps are high current, and I think Plinus is also, that's why lots of Classe and Spectral amps are demo'ed in stores with mit powercords. I use the SR masters on my digital front end and they are superior to the mit in that context. Next, I'm a big mit fan but based on my experience ic's and speaker cables should match to really get the benefit of the coherent sound you get from all mit. Go for 330 shotguns or better if you can swing it - used. I would live with that change for a few months to let everything settle and burn in. Next, If not completely satisfied (who ever is in this hobby), I'd look into a tube preamp. Good luck...

Change your speakers for stators. They are just perfect for the kind of music you prefer.