Fostex Drivers.... need some advice here..

I have a pair of Odeon Rigoletto speakers. They have two drivers in each speaker..... Audax horn tweeters and Fostex FE164 full range drivers. I want to upgrade without buying new speakers. Was looking at the FE167E drivers as replacements for the 164s. Will cost me about $120 for the new drivers. Will the difference in sound be enough to justify the cost? Any advice would be greatly appreciated!
i am thinking of buying either the rigoletto or tosca. What electronics are you using?
I dont think your upgrade would be off much use. fe167e is kind of average fostex if not a bit below average performance. Why not sell your loudspeakers and purchase a fostex based loudspeakers with a far better driver? Fostex has the all new fe138esr, this best fostex fullrange is available on audiogon at a give away price. The fe138esr is so far above the performance of a fe124e or fe127e. A $900 pair driver compared to $120.
I am using a Dared VP-845 amp, Pioneer Elite Pd-65 transport, and a Xindak dac-5. I think I agree with John about the upgrade to the fe167, but I am dying to swap to the Fostex Sigma fe168. Heard great things about those.