I have an M90z with the i3-530 processor. Earlier posts asked about upgrading the processor and the comment was made that you could move to i5-660/670. Most of these processors now seem to be unavailable. Given that it is 6/2012 (and those posts are from 2011), are there new recommendations? Will this unit support a quad-core processor? Are there later versions of the i5 or i7 series that are compatible?