I bought the Swamp Thang to replace the stock Eminence-made speaker in a Fender Blues Deluxe Reissue, as I found that stock speaker to lose clarity at higher volumes, tend towards a rather shrill high-end even with very low treble settings, and become very flubby and distort quite easily.
The Swamp Thang remedies all of these issues. The bottom end is tight and powerful and never gives in to flub (this speaker handles bass frequencies extremely well, I've played bass through it, and some rather extreme sub-frequency octave effects, and none of those frequencies seem to just "disappear" as they do with many standard electric guitar amp speakers ? Eminence actually state on their site that this amp can handle 7-string and bass guitar easily), the mids are clear and punchy, and the highs are actually manageable now.
If you're looking to retain an "American" tone for a Fender amp, whilst vastly improving sound quality and volume efficiency, I highly recommend this speaker.