For anyone who's looking into buying this amp, please keep in mind that Fender chose to put a crap speaker in it. As I'm writing this review, the Jensen C12Q is currently the cheapest 12" guitar speaker Thomann has in stock.
Fender claims that the 64 Custom is lighter than the 65 Reissue due to the pine cabinet, but in fact, most of the additional weight of the 65 Reissue is due to the massive C12K which is a much better speaker. The C12K weighs roughly four times more than the Q.
With the stock speaker, the mids sounds like cardboard with a plastic feel to the entire sound. I cannot rate the amps "sound" more than 3 stars in its stock state.
HOWEVER!
After swapping the speaker it's an amazing amp.
I own a 65 Reissue as well so I'm blessed to actually compare the two. The 64 Custom sounds even more "Fender" than the 65. Deeper low end and more shimmery highs. It sounds bigger than it is. Almost Twin Reverb-esque. It makes the 65 Reissue sound almost boxy in comparison.
First, I installed a C12K. It generated an extreme bass response, although musical and nice, but a bit much for my taste to fit in a band mix. So I put in a Celestion G12-65 for a bit more pronounced mids and a gainier character. I believe great results can be achieved with pretty much any quality speaker. Acquire to taste.
The bias-shifting tremolo sounds a lot better than the optocoupler tremolo used in the 65 Reissue. It has a more musical swell and can be set to lower speeds. However, the more saw-toothed wave shape of the optocoupled tremolo in the 65 Reissue makes the effect cut better in a mix than the 64 Customs biastrem.
As both channels are fed to the reverb and tremolo, the two channels are in-phase which means that it is possible to link the channels with a patch cable. If you do, the amp will sound a bit more lively and alert with a bit more punch.
One thing that annoys me a little is that both volume knobs has to be set to 2-2,5 before any sound is produced. This is not the case with my 65 Reissue, but it's an issue solely down to the pots themselves, but maybe Fender should have chosen some that doesn't act like this..
Furthermore, the build quality is higher than the 65 Reissue, just as Fender claims. The vinyl is more rugged and the back doors are less flimsy. The circuitry is flawless and the aged grille looks so much better than the original Fender grille in my opinion.
It actually isn't aged though. When looking closely you'll see different colored strands of threads used to make a different color of the cloth, albeit "looking" aged. The best way to do it I reckon.
All in all, a superb amp with a joke of a stock speaker. A way for Fender to cut the cost I guess.. (Frowning smiley-face)