Nick will recommend velodynes to you as thats his favourite.
The Monolith will be excellent in the right hands and with freedom to place it in the best spot.
If it has to go in a corner which is not a bad thing sealed's are easier to work with generally people say, depends on a lot of things
I think a lot of the time the bass thats missing is the upper bass. I had this problem for years - loads of low end not enough punchy upper bass.
2 things sorted this out - 1 was alignment - getting the timing between the subs and speakers spot on.
Now I mean for all speakers not just the front 2. If you get this right you can have full on explosions behind you. There is the scene in Oblivion where Cruise checks out the crashed ship with all the humans in hyper sleep. Quite soon after he gets out of his flying craft there is an explosion behind him and thats also supposed to be behind the listener to the left. - Thats class to experience when done properly. Auto setups are supposed to do this - but there is a easy way to check.
Download this and burn it to a DVD as an ISO
- or just get it to play on your blu ray player.
In the stereo section there is a timing - you hear a a tick from speaker and a boomb from sub - you adjust the speaker distances until the tick and boomb are starting and stopping exactly in time.
I can do this for all my speakers by changing the interconnects between the processor and power amp.
For those using recievers - Make sure you have the Receiver in Stereo to adjust the front 2 speakers. I would say to adjust both the speakers by the same distance - i.e. both up or down in distance by the same amount.
Then to check the centre change the system into prologic and the tick comes out of the centre.
You might have to think of a way to do the rears, I am not sure for that.
This is extremely worth doing / checking as it will knit your bass together with the speakers perfectly if it is not already.
Second is to run dual subs and higher crossovers - I am sold on this - no going back for me ever