If you have had good luck with Popo then go with them again. The years you had one were not their best and the new ones are far better. I like Suzuki and have a Kingquad 450 with IRS and EFI. The new Sportsman 500 has both these features and I understand it is a nice ride. For reviews go to this site http://www.powersportsnetwork.com/enthusiasts/review_list.asp
and under reviews there will be a drop down box...select atv then go to the mfg you are looking for. Good luck