The projectors do have an excellent built in quadrupler. Most of the content will come in looking great (assuming you have the right lens-which is a huge IF). The first time I saw DLP 4k with Barco at Showeast it was not so great, at the DCI symposium it was unbelievably sharp, then at the demonstration of another Light Source Barco projector technology in Hollywood they also had a 4k B-32 there, it was dejavu all over (soft).
In my opinion it is the lens and possibly they brought in one of the very two first units that were floating around. I want the same experience I saw at the symposium, you could play a vhs tape on that system and it would look clear and sharp. I am exaggerating but they did show some great looking directv and ps3 stuff using their own internal scaler. Unless you want to go for the P where you will not reap the benefits of double the dci color space unless you get content in the dci color space, there is zero reason to go 2k (assuming you have the right lens-a big IF -repeat).