What's better? 1 amp of 250wpc OR 2 amps of 135wpc each one?

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
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Sean, your comments does not bother me, in fact, I think you probably are right. I was already thinking of adding a powered subwoofer (for instance a rel strata III). Yes, I think the upper bass is weak currently, but I do not understand how is that by adding a sub it will "remove bass duties from the Maggies and I will free up more power for the upper bass, mids and highs"?. My understanding is that the subwoofer simply will "see" frequencies (low) that the Maggies do not "see", so the speakers will do the same (will have the same current or power from the amp) with or without the subwoofer (please correct me if I'm wrong), so I do not understand how is that by adding the sub it will ease some of the strain from the amp. Could you please explain me why. Obviously I'm not an expert on this. Thanks for the input ..jorge.

The Maggies will not be trying to reproduce the bottom end if and only if you use a crossover to remove the bass from them and pass that range of frequencies to the subwoofer. Some of the powered subwoofers have a crossover built into them and you can get the upper frequencies to the maggies using the high pass out feature. I would typically be leary of the sound quality from a crossover inside a subwoofer but it could be a starting point to see if that is the solution and then purchase a high quality crossover later.