Actually Kick, that's exactly what i'm trying to get rid of.....one spinning wheel, which is caused in this case by an open differential (the stock unit)

Here's Basic Differential 101. Differentials come in 3 basic flavors:

Spool - We don't need to concern ourselves with spools, as they are a locked axle that doesn't allow for differential action at all. They have specialized applications such as oval racing where tire size stagger can be used to compensate for the lack of differential action, offroad, where the driving surface can slip, etc.

Open Differential - this is what comes stock on almost every grocery getter in the universe. By means of a gearset, it allows the inner and outer wheels of a car to travel at different rates, , however, if one wheel begins to spin, it will happily apply all of the motor's power to that one spinning wheel while the other wheel remains effectively motionless....BLEH....BAD.

Limitesd Slip Differential - While maintaining all of the functionality of an open differential, the limited slip goes one further. In the event of a single wheel breaking traction, the differential transfers power away from the spinning wheel to the one that has grip. This is generally accomplished by one of three methods - clutch packs that are engaged more and more as one wheel spins, a worm-gear systems, as in the offerings from Quaife and Torsen, and the factory R specification viscous coupling LSD...bastard cousin of the torque converter. Regardless of the means, the purpose of an LSD is 2-fold: 1) offer differential action so that the inner and outer wheels can sustain a speed differential during cornering (outside wheel travels further than inside in a turn), and 2) to control single wheel spin by reducing the power being applied to the spinning wheel and applying it to the wheel that is still "hooked up".

Since my T5-r likes to eat rather expensive rubber and isn't living up to all of it's potential, I am looking for a limited slip for it.

Sound reasonable?

850's in general and T5-r's in particular have problems with both torque steer and the resultant single wheel spin. There is no point at all in trying to increase the output of the motor if you simply spin one heel like mad when trying to launch hard - be it from a stop or off of a slow corner