In MY opinion, i can see how you think the system is "thin". From my experience, ALL of your components are on the "lean" side. While MF gear is not "harsh" or "bright", it is definitely NOT warm, full or "powerful" when talking about tonal balance. I would call it "quick and clean" but lacking in "oomph" or "body". While my findings with Analysis Plus speaker cables tend to go against the grain, i found them to be VERY lean sounding with a bright, tizzy treble. This was using a set of the Oval 9's that had WAY over 500 hours of time on them. I can't comment on their interconnects, as i've never tried them. Your speakers, as you probably know, are not known for exhibiting great amounts of "warmth", "body" or "weight". On top of this, they can be more difficult to set up in a room due to their radiation pattern. As such, the things that take the biggest hit in the nose when not perfectly dialed in are the soundstage, imaging and bottom end.
With all of that in mind, i don't think that adding another amp is going to give you what you want, especially if it is another MF ( regardless of power rating ). This would only give you more power to avoid "stress" or "strain", but would NOT correct the tonal imbalance problem. The REAL benefits of bi-amping come from using an active crossover and bypassing the passive crossover of the speaker. This means that you would need both an amp, an active crossover, modifications to your speakers and a LOT of dialing in.
If your basically happy with everything but want more "weight" to the sound and would like to ease some of the strain from your amp, i would think about adding a powered subwoofer. Not only will this give the music more impact and foundation, by removing bass duties from the Maggies you will free up more power for the upper bass, mids and highs. This approach may "kill two birds with one stone" ( sorry PETA fans ).
Other than that, you might have to re-assess your system on a component by component basis and see where the weak links are and what your overall system goals consist of. Sorry if this sounds kind of harsh, but i'm trying to offer "honest" advice. Others may or may not agree. I hope you take this in the light that i'm offering my comments. Best wishes... Sean