You might want to re-think the issue of Xrays on the PPE if you're planning on doing much jumping. My first horse (that's him in the userpic) is a retired show jumper and has some major thickening in the joints of his front legs, and possibly a little arthritis as well. I passed on the Xrays because when the vet said "don't jump this guy higher than 1 foot, unless you want to be feeding him bute" I took it seriously, and he's presently getting a second career in dressage. Something a little less hard on the legs. If I'd wanted to jump him, well, I probably wouldn't have bought *this* horse because he's just had a ton of wear and tear from jumping...but if I'd been looking at a horse for jumping, I would definitely have wanted more info about the state of his joints than could be got by a visual and physical exam.
What I did do - even though I was not at all concerned about the possibility of doping, because this guy had been my lesson horse for a couple months before I bought him, and if he was getting doped for the sale, it was happening on a daily basis before that - was to get the blood panel. This added a hundred bucks or so to the cost of the PPE, but it is well worth it! Not, as I said, because I was worried about doping, but because it would provide early warning signs of metabolic disorders, etc. - and in the event that there wasn't any of that - it provides a good set of baselines for him. Now, if he gets sick and the vet has to do a blood test, we know what his "normal" is and that will help us identify what is *not* "normal".
One other thing is that you should not be getting the horse's regular vet to do the PPE. There's a conflict of interest there. It's a good idea to get a vet that isn't familiar with the horse - that way, they are less likely to overlook something that might be of interest to you (which could happen if they know the horse, and they're already aware of Problem X and don't consider it to be a big deal, so they don't really think about it. This doesn't mean the vet is "bad" - it is a basic human information processing problem...they can't help it. That's why it's good to get a fresh set of eyes.) Also, when you go to check out the horse, look at it for any signs that it's been worked recently (sweat ripples, etc.).