Bill,
The Jordan JX92S is a very nice driver when used alone. Like most speakers you will need a little baffle step compensation (BSC) to balance the sound. The JX92S would certainly be a step above the Fostex 103E.
While the Jordan driver does several things well--nice bass extension in a reasonable sized vented alignment, acceptable full range performance, etc--it does have some shortcomings. There is some beaming and a bit of roughness in the upper octave (10-20 kHz) as you will find with most full range single driver speakers. The JX92S speaker is not as sensitivity as one might like and the BSC reduces sensitivity a bit more (say in the mid 80's DB SPL). I would suggest that you will need to have 20 watts or more per channel to get the best from them. They work their best in a small to moderate sized room.
I'm not much on the Jordan factory TL plans as you can not get chest thumping bass from a driver this size with any bass alignment in my opinion. My vented mini-monitors have enough extension (down to low 50's Hz) and it is so easy to pick-up the lowest octave with a true subwoofer that I suggest that you aim in that direction. Now Greg Monfort (GM) has a Martin King spread sheet mass loaded QW design that some folks have built that is supposed to be very good although I haven't heard them.
The Atlanta DIY winners (Jordan JX92S with Aurum Cantus G2si ribbon) are a definite sonic miracle in my mind. A 0.3 cu. ft. speaker that goes down to a 51 Hz F3 point for bass. The airy sound of the ribbons for the highs really helps their character. They are lightning in a bottle (or a box in this case) with a wide soundstage and a nonfatiguing character that makes you enjoy them for hours. I've built small speakers and large ones (line arrays) but this is most my most enjoyable design.
Bottom line is that you will be happy with the JX92S single driver speaker but you would really love the JX92S with the ribbon configuration.
Jim