Yes the 7 speaker system will work with that harness and deck.
Funny enough I still have the packaging for the dash kit. I got it from Futureshop's Car Audio install department (they gave me the wrong harness when I first went in and then told me I couldn't do a aftermarket install on an XLS without rewiring the whole speaker system...idiots, but the kit was correct!)
The brand is "Best Kits and Harnesses" and the serial # is BKTN2150B.
It works 'alright', but it could fit a bit better ie: less gap, better match with the other plastic around dash, but its a universal kit, so...
Look around for a kit with smooth plastic pocket, mine has a texture(see pic). Also there is very little room at the top of the radio (because of the Avalon's trim) so your radio's trim ring will most likely not fit.
Good luck!