Let's say, for curiosity's sake that you could beef up your arcane ECL far beyond what it normally should be.
Your actual CL and, by extension, the maximum level of spell you can cast is still restricted.

-Rules-
It has to be arcane.
It can be 3.5 or PF

What, in regards to class, race, feat, etc. is the heftiest bang you can find for your considerable buck?
How do you take advantage of this?