Side speaker importance

Hello from the Holly Land :-)
i have Lexicon MC-8 processor with a 6.1 setup (no center speaker) which i use for movies only (no m-ch music).

the full system spec can be seen here:
http://cgi.audioasylum.com/systems/4657.html

i have pretty cheap side speakers Mission M71 which costed just 250$ at the time (stereiophile review http://www.stereophile.com/budgetcomponents/511/index.html ).
they're placed a bit behind seating position and aimed to the listeners' ears.

in a stand alone system they produce quite nice sound but when i compare them to my front speakers they just sound awful - much less details, clarity, air, etc.

the question is - is it worth to invest in side speakers?

another one - since my armchairs' backrests are quite high (IKEA Puang) - about 80 cm - i put my side and rear speakers at 80-90 cm height.

in this situation is it better to keep "bookshelf speaker" path for the sides and elevate them to this height or go to floorstanded and gain some sound depth and bass extension but compromised on a fact that some of it's drivers will be placed low and thus concealed by the chair's backrest?

some room's photos can found here:
http://photofile.ru/users/croc999/1164416/

thx in advance,
Gennady