New blood needs your Amp/system advice, please.

Greetings, Fellow Enthusiasts. This is my debut post on any sort of hi-fi forum. Excited to begin tapping into some of your knowledge/expertise.

I am slowly trying to piece together a clean, simple and very musical two channel experience. Cut my 'Seperates' teeth on a Rotel system about nine years ago... good entry level gear. My pre-amp recently died and I started a pupae phase of more critical listening and put together a few new pieces.

current system:

power plant: PS Audio PS-600

pre-amp: Audio Research LS3

cd: Naim CD5i

amp: Rotel RB 981 {120 wpc}

speakers: Paradigm Studio 100's V3.

speaker cables: Transparent "The Wave"

interconnects: Interlink "The Link" 200

The system sounds okay with vocals, guitar and horns etc. but is fairly flat and muddy in much of the mid-lower ends. It's seems obvious that these speakers are severely underpowered. Is this likely what I am hearing? What steps should I take to attain more balance in this system? How much power would be enough?

What Amps would you recommend?

Got a great deal on most of this gear and am still auditioning. Am not really married to any of it and am willing to consider replacing to gain a more musical enjoyment.

Thanks in advance for your time on this.

Cheers! Timothy