Blocks also make it easier to diagnose electrical issues, but I don't think you need it for that layout, especially where you are not running DCS.
You might want to check out the MTH Z-4000, which is little on the pricey side but which offers some nice benefits. First, there are two separate track out puts, each controlled by its own throttle. That mean that you could electrically separate at least two of your loops, each with its own power supply. Put the longest on one output and the two shortest on the other. It also doesn't produce a chopped sine wave. It also has two accessory outputs for buildings, structures, lights, etc - one for 10v and one at 14v.
Finally, no matter which way you go, you should consider (a) putting in plenty of power drops to the tracks and (b) putting the yard and/or each siding on a separate switch.
