Upgrade Advice

Hi All

Looking to upgrade my audio/HT system

I have:
Denon AVR 4311CI
Mirage OS-FS (v2 I think) for fronts
Mirage Omnistats x 4 for surround L+R and Front Wide L+R
Mirage nanosats fore rear
Mirage OS3-CC center
SVS SB13-Ultra sub.

I love the sub and am planning a second.

I use it for HT 80% of the time and music 20%. Music source is normally lossless rips of CD's or downloads from iTunes via Sonos to Denon via optical. I listen to mostly contemporary music. Have a few SACDs (Sony S790 Blu-ray)

I would like to lose the floor standing speakers because of space/aesthetic issues and replace with good quality bookshelf speakers that would work well with the SVS. Given that the sub is always used, will I miss much doing this? I do have a pare set of the Mirage bookshelf speakers

Also considering separate power amps like Emotiva XPA-2. Is this pointless with bookshelf speakers? Would better amp be better than better speakers (given the speakers I have)

What would be best upgrade for a few thousand now and some more later? Should I go with external amps first and then new speakers or vice versa?

I can live without the rear speakers, as there is very little content in 7.1