Kartingboy,
A few words on the options you are looking at...
A wide-band (also known as "full-range") driver will have it's limitation in SPL output (how loud it can go), and frequency response (how much of the frequency range it can cover), and is likely to have some unevenness in the response too. But all is not lost
, they can still be enjoyable with certain genres and at reasonable SPL levels (depends on person to person preference and room size
).
The Fostex model you have mentioned is an example of a wide-band driver. I have some experience with an older driver, the FE206EN, and did not like it that much. I found that Mark Audio drivers can be installed in simpler and smaller cabinets, and cover more of the frequency range on both high and low frequencies. The sensitivity is lower vs Fostex, but still can go do loud levels with tube or low wattage amps.
There is also a new SB Acoustics wide-band driver that is supposed to perform well with a simple BSC circuit. There is a 5" Tang-Band unit with paper cone which folks have found good too.
A word of caution, in my experience tube-amps paired with single wide-band driver speakers can handle less complex and lighter musical genres at reasonable levels quite well; there might be some coloration to the sound, but many find them enjoyable. With heavier genres (like rock, metal) my experience was not so good.
Hence I had an earlier post asking you about your preferred genres/types of music.