Well, I have a mostly metal/prog-metal background, which I only got into within the last few years, so take what I have to say with a grain of "metal" salt.
Check out Haken - Aquarius. It's about one third metal, two thirds hard rock, and 100% prog. It is, hands down, my favorite album of 2010. They only have the one album so far, but they are destined for greatness. If you claim to like prog, you must at least try this album. I literally listened to this every day for at least a month.
Another one I recommend: Forgotten Suns - Innergy. Their earlier albums were prog-rock. However, Innergy ramps it up by working in some metal, and like Aquarius it combines the best elements of both, while avoiding most of the more obnoxious aspects of metal. Don't get me wrong, I mostly love metal, but some aspects of it (especially the drumming), drive me nuts after awhile.
Also, I hate to say it, but you can count me among those who could never get into Porcupine Tree