For headwind distance, I still use my CPD2. I'll use my preds into the wind for anything but max distance though.
Getting good distance into the wind can be tricky. You have to be comfortable with your throw and your disc. You have to be able to throw your disc hard still, with the nose down, and trust that the disc will not turn, or will not turn too much.
As far as disc selection, faster discs should be able to penetrate better into the wind. Throwing into a headwind means that you are increasing the relative air speed of the disc compared to the same shot with no wind. Discs will turn easier and have less fade in general, assuming you are throwing the same way. The downside to throwing faster discs into a headwind is that they are also more nose angle sensitive. If you don't get the nose down enough, the wind can really punish a throw with a faster disc, usually causing it to lift, then fade out early. My first guess would be this is what is happening to your shots into the wind.
More overstable discs will allow you to be more comfortable throwing into the wind without the threat of turning too much. There is a distinction between a truly overstable disc and a speed stable disc though. A truly overstable disc (most common examples would be firebirds, predators, XXX) is going to have a similar stability over a wide range of air speeds. Speed stable discs typically refer to the warp speed discs that, when they aren't thrown with enough speed, behave very similar to your truly overstable discs, but aren't a really a "reliable" overstable disc. (Yes, I realize that any disc can be considered "speed stable" if you aren't getting them up to speed. Fast drivers (Innova speed 12 and 13 is what I usually think about) are usually the ones that are thrown into this category though).
Its been a while since I've thrown an Xcal (and I've never thrown a champ xcal) so bear with me. I've always considered the xcal to be in between a truly overstable and speed stable disc. It does have overstable qualities to it, but as a 400'+ thrower myself, I could never trust it into a headwind because it would still turn too much to be reliable to me. The PD2 is very similar to the xcal, but is more of a truly overstable disc imo in C or, from what I hear, S plastic now. (PPD2 are great discs, but not the wind fighters the premium plastics are). I've been intrigued by the giant as well lately to though. Of course, like others have mentioned, slower overstable discs will be useful to you as well, as they can reliably hit 350-380' into the wind VERY reliably.
However, a truly overstable disc will not help you if the issue is you throwing nose up into the wind. On your shots into the wind, what is the flight of the disc like?
P2 - Fuse - ROCS!!! - QJLS - QPLS - QOLS - PD - Predator - Quasar