Stratix IV devkit recommendations?

There is S4GX PCIe devkit as Altera product. As you may know, it comes with PCIe edge connector, so it is ready to use with PCIe interface.

The device on this board is either 230 or 530. If you do not need PCIe, then you can go with S4E devkit, which does not have transcivers on the device, but it is huge device.

Both S4GX and S4E devkit, you can put Emb-Linux on it. I put Linux on the S4GX board while ago. Basically, the requirements for the emb-Linux is more than 8MByte of off chip memory and ideally, CFI-Flash, and ethernet. Both boards have them.

I do not think Altera is supporting Linux, but you can find most of necessary information to build Linux at here or at Altera wiki.