Don't do it you will not like a solid unspeng disc in an all wheel drive car i have driven unsprung disc's in evo's noisy, harsh engagement, horrible for your drivetrain in general.Remeber these car's don't just send power to the front wheels or just the rear, they send power to all four of them.
Harsh engaugement will be that much harder on your drivetrain transmission,transfer case, drive shafts,and rear differential.

 

Have you even looked? RRE and Gruppe S both have good clutches for the Evo under $500, and two of them are Exedy, the others ACT. The eBay clutch you linked to is only about $100 cheaper.