There are sooo many threads on here about soft luggage. Search under soft luggage, luggage, panners. I have been researching soft lugage too and it sems that Dirt Bagz are very popular ($219.00 for luggage and rack) and Wolfman and some company from Austrailia.. Andy something..
The Happy Trails will work with everything but at $200.00 just for the rack you can buy an entire Dirt Bagz set up. I like the way RKA's look and all their features are nice but I only know of one other guy using them.
TT are a no brainer but it all comes down to personalopinion. I love me stock KTM pegs, I just removed the rubber pads.
I am usually drunk when I post so dont take it personally !
2010 KTM 990