I believe all Sandybridge core i3/i5/i7 CPU's work fine in the 4530s. Just make sure you stay away from ES (Engineering Sample) and QS (Quality Sample) chips. They may be non standard or have instructions missing. Also, if you put a chip in that is not included in the Probook Installer, you will have to create or modify an SSDT file to work with yours. Im running an i7 2670qm. I get a feeling that the best chips for 99% of us are the mid and upper i5 range. They use less power, make less heat (read quieter fan) than the i7's and hardly anybody needs 4 cores.
Have a look at th comparison on wikipedia:
http://en.wikipedia.org/wiki/Sandy_Bridge#Mobile_platform