Speaker design for guitar is really a personal matter, so there's no right or wrong answer. If you get the sound you want, its right. If this were sound reinforcement or reproduction you would likely seek a flatter, uncolored response.
Having said that, the low end in the proposed system will be less than it could be. Baron030 already pointed out the the output drop below the mid 100 hz, but there's also a difference in sensitivity between E140's (100db) and E120's (103 db).
http://www.jblpro.com/pub/components/eseries.pdf You will have to think about the difference in volume of what's coming out of the E120's and the frequencies rolled off by the E140 cabinet. If you play harmonics on the G B and E strings on the seventh fret or above, those tones are going to cut through the mix. The crossover point will make a difference as to where the difference in volume occurs, but doesn't necessarily solve the problem.
Again, whether this is good or bad, isn't decided on paper. Its up to you and your audience.
You could add attenuation to the crossover to give it flexibility.