Hi Lee
I would go with the Shure SE535 or the SE215

The 215 offers a big leap in performance over similar priced EP\s and certainly over the ones supplied with phones........the 3's and 4's are nice, but incremental upgrades.......while the 5's offers another big leap........all are easily driven and match well with the Explorer 2

The Sennheiser IE800 and especially the Shure 846 are also very impressive........but you would need to find these at the right price

The Westone's are also worth a listen.......but I think the Shures match better with the Explorer

-