Front and rear port firing design, and also the height. Rear port firing usually benefit for adjusting the bass volume by positioning close or far to the wall.
For your budget just try to get Studio 6 or Studio 7.
Studio 7 yes is really sound different from Studio 6 because it implement midrange driver to further reduce the distortion which normally a 2 way speaker will suffer.

AFAIK, the influence with room changes it. But I myself prefer front firing port because I feel that I can get a much tighter bass easily in my room.
Yes, the bass on Studio 7 is clean and clear on any music. If you feel the bass isn't enough there is a bass knob there to turn up 
You can try out the demo unit at any shop that sells R2700 see whether you like it or not.
But remember when you just got your speaker, let it run in by playing music loud for weeks normally to get the optimal performance from the speaker.

Yes you can, but the subwoofer I suggest it should be able to play low note like down to 30hz, else you will get much more thumpy bass instead of good more loud and fuller bass.

They were expensive, many times more than the Studio 7 price   
If you afraid that it really lack of bass you can look for Studio 8, it has 8 inch bass drivers which should be sufficient to most bass heads.
But always remember to test the demo set first before you get one.

where are you located?? cause Sri Com in LYP has the full range of Studio series lined up for testing and also MVP Concept store has the full range as well

For me I think the mids and highs are about the same, just mid low to low there makes the difference. Normally Studio 7 is sufficient to close listening with good bass, R2800 capable to put at living room.

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