Depends on your tolerance for sitting in back if worst comes to worst. Normally the most economical route is to buy Y and watch for upsell offers. Sometimes straight to J, or sometimes to lock in PE at a sensible price and then wait for another compelling offer to jump up to J (especially if the difference is huge). Currently on one of my TATLs, the buyup offer to PE is $1,100 while the offer to upgrade straight to J is $1,200. They're starting to get desperate because a week ago it was $1,800 for J and $600 for PE.

If you absolutely must not sit in back, you're going to have to lock in on something. Playing the waiting game can cut both ways.