You know all the guys that compete professionaly, want to get their bass up front. They go through all sorts of lengths to do this. Here we have the NSX that has a sub where it belongs, up front, and now you want to move it to the rear?!
The front is the best location sonicaly for a number of reasons. Also Hal has gone through the trouble and save everyone a lot of time and money by custom fabricating a nice well-fitting, excellent sounding box that fits flush and is not seen.
You can spend double the money and it may be 'different', but I seriously doubt it will sound better, in fact I am almost certain it will be worse.
You obscure your view, you have a woofer too close to the head, it is in a location where it does not couple to the body like the front unit, phasing becomes more of a problem.... and honestly, I think it looks terrible (but thats personal).
Save yourself the headache and get Hal's box and be done. :smile: