Underwhelming sound from Onkyo 606+polk system

[Cpus456]

My problem seems to stem from a lack of power.

I think the addition on my 2xRTI10's, then the CSI6 have put a strain on my Onkyo.

The unit pushes 90 watt per channel and every channel is being used.

yesterday i was reading that my rti10 are actually 4 ohms [with the straps on(read in a polk audio forum and was confirmed by on tech at polk)

Also my CSI6 is running at 6ohms.

This added stress must be the reason my sound seems err, umm Empty! if thats a way to describe it.

The fullness is not there!

now the solution might me to add an amp to power my 3 front units - but the problem lies in the AMP - no pre outs to an external amp
Should have opped for the 707.

I also read the the emptyness might be due to the fact that im using onlyo with my polks - the onks seem to have that effect on them

Heres some info about my setup

Placement:
Open concept condo
Room is about 25x20
Concrete walls
My Front Left and surrond right are up against a wall (see pictures in gallery)
the backs of my front speakers are sitting pretty much against a wall
https://images.blu-ray.com/htgallery/21951_full.jpg
https://images.blu-ray.com/htgallery/21955_full.jpg

what should i do

go the cheap route and remove the straps on my RTI10, disabling one of the 8 inch woofer so they can run in 8 olms and disconnect my two rear speaker and go 5.1?

or

Sell my onkyo and grab a pioneer elite VSX-21TXH and a 3 channel amp to power my front stage.?

or

Emotiva UMC-1 and UPa - 7

Recommendations?