Help with spacer and handling question!!!!!

[pachanga231]

got a b5.5 tdi sport lowered on fk coilovers on standard sport alloys. the rear wheel sits inside the arch more so than the front i think the rims are et37. im not going to upgrade to 18's etc so i was thinking of putting some spacers on the rear to bring the rim in line with the arch and same on the front, this would hopefully give the car a slightly wider stance and i wanted to know if it would improve the handling in any way. would it be safe/beneficial to do this and WOULD it actually give the car a wider stance. anyone recommed size of spacers 10mm rear??? 5mm front. can i just go with cheap ones or is it better to go for the hubcentric ones that bolt onto hub......finally need to get some tyres 205/50x16 had toyo t1's not been that impressed, heard good comments about dunlop sp9000 or they just good for stretching need summat practical with solid grip
thanks peeps.