If your local Authorities allow, you might be better off looking at a slightly different size for the Rear kongdoly!
Here in Oz, we are allowed to fit different sizes/tires within a certain range, just so long as they meet or exceed the Load & Speed ratings of the OEM tire; effectively meaning that if it's an approved/allowed fit on your Spyder's OE Rims and the tire you choose will fit under the OEM Fenders without rubbing, you can run it! I've tested quite a few tires on my Spyder and I'm currently running a 205/60R15 Michelin on the back of my Spyder RT that's working very well on our 'less than ideal' road surfaces! So if your Authorities work on a similar basis to ours, then after looking at the selection of tires you've got for the front, in
your circumstances I'd be very tempted to go with Michelin XM2+ tires all round!
The Michelin XM2+ 175/50R15's you list will fit and work very well up front, altho you might need to just ease up the lip of the fender a touch to actually put them on, but they'll fit fine once mounted; and you should also check to make sure they don't rub the black inner fender splash guard or the heads of the bolts holding the fender on - you might need to swap the hex head bolts for flat head or pan head screws - I have.
A 205/60R15 Michelin will easily fit on the rear and will probably make your speedo a lot closer to accurate too! I'd expect you to be very pleased & impressed with the improved ride & handling running about 16-18 psi all round!
Mind you, I don't know what the difference is, but here in Oz the Kumho you've listed works far better than the OEM tires all respects, they last pretty well on our hot roads, and they have none of the hydroplaning tendencies in the wet that some have reported experiencing in North America - maybe it's our coarser &/or hotter road surfaces, or possibly we get a slightly different tread compound here??
But
IF yours are anything like ours, then when run at or near the right (lower) pressure for the (lighter) load of our Spyders, you could do a lot worse than running one of those Kumho's!