i have a set of stellings and xr's for sale on classifieds, like new

I had a Stellings on my old boat and they are bullet proof. The transom or gimble will fail before the box does. If you do go with the Stellings, open up the bolt holes so you have slots. This way you don't have to disassemble the transom assembly to adjust the X. You'll want to use the Stellings inner plate, but don't go nuts on the torque. I overtightened mine and crushed the transom. I figured it out when the motor mount plate wouldn't drop in because the ears and shifted inward. Things never did fit right after that. With the Stellings you can do a drive alignment with a standard too. You need a special IMCO tool align the imco box. You also need to change the drive shaft to the longer IMCO shaft. This could complicate things if you frag a drive and want to get back on the water. IMCO makes the arms so their steering can be mounted right on the Stellings box.

Imco 4x4's are rated for 900hp. They are 1/2 the weight of the Number Sixes and can be installed in place of a Bravo on the transom. I have a nearly new set (take-offs) from a MTI cat that would be perfect for your Spectre. If you are running any kind of power you will need to step up from the Bravo setups. HOT deal on these.
http://www.offshoreonly.com/esvon/page-7562.html