the crucial M4 will be fine. it was what i was going to get before my new rig build got delayed and then the intel 330s dropped in price.
The difference between the 840 Pro and the 840 is that the Pro uses MLC technology (Multi-Level Cell) which basically means there are 4 voltage levels or 2 bits worth of data held in each transistor. most SSDs are this way. The normal uses TLC (Triple-Level Cell) which has 8 voltage levels or 3 bits worth of data held in each transistor. the fear is that with a much lesser voltage range in each transistor to differentiate 3 bits, the SSD will not last as long - however initial stress testing suggests the regular 840 will be fine still.
The TJ08-E is a fair bit smaller than the corsair 350D, however the SG08 and the Node 304 should be another level smaller again.http://www.overclock.net/t/1068487/silverstone-tj08-e-owners-club/3500_50#post_19185224
these were the pics i posted of my TJ08-E. let me know if you want any other photos. definitely going to be bigger due to mATX design instead of ITX.