Hi Michael
thats a really clean looking install and I like the cabinet, your carpentry skills are very good
If you are thinking of changing it around then why not try something like this if the fire isn`t used for heating but just as a feature
this still allows you to mount the panel at a lower level for better viewing angles and won`t be compromised with heat travel, anyway just a thought Michael.
The position where your sub is can be a bit tricky as its being excited with being in a corner, I know its not always acheiveable to have it in "the prime position" but it could be sounding a little "EXCITED". The sub in any AV install is always the hardest thing to get right, positioning it will always help but its not that simple especially when other things like wifes and girlfriends come into the aquaision lol.
However that is always the first course of action I would take if allowed to, if not, some sort of room EQ would i`m certain be of help to you in controlling the sub and how it sounds. I would if this is a newish install though take a little time to get used to how its sounding and see if you can settle with it, if not then it can be easy, if you go the right way to help the room and the equipment within it to gel together especially in the LFE dept.
there are numerous ways like using REW and a BFD which is a less expensive option but can be very time consuming and obsessive and only if you`re a tweaker which I definatley aren`t, or you can used something like an antimode 8033c which is a 5 minute solution to many LFE EQ problems.
Anyway once again its a class install and one to be proud of, well done
Al