Your talking my language bro. Our systems are very similar.
I run Maggie 1.6 and CC3 center. Rear channels are just bookshelves from years back, but eventually want to get MMGW's for the rears when I get moved into a different room with more space at the back. Subwoofer is a $500 Velodyne for right now. It is only in the system for Home Theater and not 2 channel. Maybe someday a better one.
I run McCormack DNA 1 with a hot rodded (TKD stepped attentuator)passive FT Audio LW1 preamp. My McCormack DNA 1 is not modified or "hot rodded", but my front source components are. (When I speak of "hot rodding" I am speaking of making physical changes to the gear, not just isolation tweaks, etc.) I heard a McCormack Rev. A modded amp in another guys setup, and while it was nice, it was not for me in terms of what my system is already producing sound wise. Do not overlook room acoustics. I am shocked with how many audiophiles forget that the sound we hear is influenced by the room.
It has been my experience that a person can "Tweak" a system too much. In other words, some tweaking is very good, but do not tweak every component in your system electronically. My experience there has been that one can "overdue it" resulting in glare, and a sterile unemotional sound. I would say, do the amp, or the source component, but not both.
Many audiophiles are really into the "Recessed, wide open, transparent" sound. For me, this impresses in the short term if you haven't heard it before, but is not emotional enough. (Vocals do not sound present and intimate.) Your Maggies have far greater potential!! (Write me for infomation on bass trap placement, and other info if anything here interests you.) Transparency is a big issue for me also in terms of creating the sense of "presense" and 3D layering. But not a recessed sound. Many mods create this more recessed sound, and too much of it, will leave your system sounding unemotional.
In detail, my system yields a more up front presentation, as if the performers were there in the very large room with you (even though the "room" is just my spare bedroom). It leads one to believe that you are at a large night club and the band is playing for a crowd of 500 people rather than sitting in an auditorium, and you are seated in the second balcony looking out upon the crowd of 2000 in front of you. I like this more intimate presentation, and up front vocals, while not losing any width and depth to the presence of the band or drummer in the back (layering).
This is getting long and windy here for all the details, but I use a receiver also (currently Rotel 1065) with Preouts for the main Left and Right channels to the McCormack using the Multi Channel direct inputs for Home Theater. This allows one master volume knob for the whole system when watching DVDs or Music Videos. When running 2 channel stereo music, the signal skips the Rotel and just runs through the passive pre and to the McCormack amp. Your Arcam AVR300 should be able to perform this same task, and is probably even better sounding than the Rotel. Do not dismiss it, and possibly look into a passive pre to add to your system for 2 channel?? Steve McCormack is a huge fan of passive pre's and his amps are designed to work very well with them. Call him and talk to him at SMc Audio. He is very knowledgable and honest.
As a side note, I have not had good experiences in tweaking my Maggie speakers. Again, my front end components are already modified some. If my front end components were NOT modified, then maybe tweaking the Speakers would help??? I do not know. I was not impressed with the IsoClean fuses recently, and I even just use the cheater U shaped bars in the back. I tried other wires there, with no good luck. Maybe it is just my setup??? I tried tiptoes under the speakers. No good either. I know hard to believe, as I expected better results also. I do use tiptoes and other isolation in other areas of my system though, and good old maple wood has proven a friend also.
Take care,
R.