Athena had a few good kits for my old DS650. Lots of satisfied builders out there. I think thats what I have for mine too...though the head gasket is a comitec for 720 pistons.
Vesrah is consistently good too. Worked for my 550F and the Ascot Rat build. My buddy got the kit for his xv920 too. I seem to recall having one issue with the exhaust washers. That might have been on the yzf450 though. Got sent a coated fabric washer for the exhaust wasn't even the right size. So had to snag an oem part for that.
All in all, vesrah seems to fit well. Albeit slightly different material than oem on occasion.