I don't own that class of machine but recently ruled them out when looking so you might want to take my advice with a grain of salt.
From my observations, the X5 series is a garden tractor and while I suspect owners of them love them, it is my opinion that they are not a good value for the dollar. While they are similar in size to a BX, a 2210, a Massey GC2300 or a New Holland TZ series tractor, that is about all they seem to have for similarities. Simply put, as a small tractor the BX, 2210, GC or TZ simply out tractor the X5 series. The X5 series frames are lighter, hydraulics lesser and I suspect their traction is also lesser as compared to the Sub-CUT class machines.
But all that said, your mowing being the biggest priority, it is hard to go up too far in size without actually having your mowing slow down because of the lack of manuverability. So that means an X5 series tractor might be a good choice as long as you don't have much tractoring to do in your future. The ROPS will give you some level of grief if you mow next to small or ornamental trees because the branches will hit the ROPS and potentially break your branches.
The FEL work in your future, as well as dealing with a gravel drive would lead me to a tractor larger than the BX, 2210, etc (but not much larger).
So then I look at what you really have, you have some jobs bigger than the X5 (FEL + blade work, because while you might TECHNICALLY be able to do those things you really will find the machine lacking compared to anything else available) and one job that is well suited to the X5 (mowing). But the X5 is nearly the same price, hence not a good value for the $. By my logic, that means you really are looking for a compramise machine, and it is harder to find a better compramise that the Sub-CUT class of machines so your options of a BX, 2210, etc are probably our best options because you will find that while they are small, they are very rugged little machines that are capable of doing big jobs. The biggest problem you will have is with the ROPS and that is only if you have small tree issues. The Sub-CUT class of machines are very good mowers. There are 4 premium machines out there (named above) I would strongly suggest you find dealers of as many of the brands as possible and play with the machines. Be as color blind as you can be and find the machine that fits you best, has the best capabilities for your tasks, and has a dealer that you are comfortable with because he treats you well and will be able to give you support. You might want to consider the Cub Cadet 5000 series as well, but I'm not personally familiar with that unit.