Some classic *mainstream* K-Pop suggestions for you because I think you’ll actually have something amusing to say about them:
5-membered TVXQ were considered powerhouses of mainstream Kpop in Korea and Japan. A personal favourite is Wrong Number (http://www.youtube.com/watch?v=rwagNDrh1DA) but most would probably recommend the fanservice-y Mirotic. Purple Line and Survivor are worth checking out. Some other ones are amazing songs but their fashion would require you to give them some slack, particularly earlier singles like Rising Sun and O.
Wonder Girls – Tell Me and Nobody dominated back in the day and were responsible for the earworm trend. Girls Generation’s Gee and Genie were of much better quality than their more recent releases, as was Super Junior’s ‘Sorry Sorry’.
Lee Hyori’s U Go Girl was pretty much the forerunner to Hyuna and just really, really fun. BoA and Epik High are also worth a listen.