Altera FPGAs in High Performance Computing(HPC) Applications

SRC Computers is the company I've heard of for# 4. They were started by Seymour Cray and do a number of different accelerator-type products. Also be sure to investigate the development side, i.e. hardware/software interaction. If you're ready to write HDL, it's usually not a big deal, but a lot of users investigating this area only write C for processors and want to "push a button" to create hardware from their C.