I've got a lot of experience with Tenecor. I have a simple 550, a marine ready 150, and a simple 50. I've had other Tenecor tanks before too, and am happy with all their products...with just a few qualifications.
First, if you go for a full stand and canopy system, be aware that their canopies do not allow enough clearance (in my opinion) to allow for much choice in lighting systems. I would seriously consider hiring someone to build a stand/canopy system.
Second, do not assume that there will be access holes on the top of the tank for heaters or filter intakes/out takes; be sure to ask for a schematic of the tank top and ask them to drill in an extra hole or two if you think you may ever need them.
As for your question about the simplicity system, I serisously considered going for one. In the end I decided that the swimming space my fish would lose relative to the convenience of having the filter in the tank just didn't make sense for me. Unless your ceiling is very low, you should be able to set up a sump below your tank instead? Also, I have seen one simplicity plus system for resale (200+ gallon) and was struck by how messy it looked. That is not really a serious criticism I guess, but it still contributed to me deciding not to go that route. The thought of having to clean out and/or ever retrofit a simplicity system somehow did not appeal to me.
Concerning your order for a Tenecor, have you considered trying to arrange a group import for your immediate area? I have done a couple group imports and found they are a great way to greatly reduce the shipping cost and negotiate further discount on the overall order. I will contact you by pm with more details.
