"Any expert opinions on these vertical Marty subs? Are they going to give the same performance?"
vertical or horizontal will have some different effects in how they work with the walls/floor etc. and it can't really be said that one will be better than the other. so as far as a rule of thumb, the performance will be the same whether upright or horizontal or even sideways as in the Cyclops design.
Well I got the enclosure together finally. Sub is mounted in it and ive been playing with it since late Sunday evening. Playing test tones it went as low as 14 hz, after that it just sort of dropped off. Much better than my dayton sub 1200 which was dropping off at 28 hz. I ended up using an ultimax 18 in this box instead of an ultimax 15. This sub is supposed to be going into my living room but im having a hard time going back to the sub 1200 in the office after having heard this one. Ill probably end up building a mini marty or maybe a cube now.