6x4 rectifier question

Probably. Changing the rectifier tubes on my power amps make an easily-heard difference.

I would say yes, as mentioned above the rectifier tube is where I normally get the biggest upgrade. I own a Lamm LL2.1 Deluxe, haven't swapped out the rectifier in it as of yet as there didn't seem to be a lot to choose from but did change out the 12AU7s to the Psvane Premium grade 12AU7T II tubes and really like them. Enjoy the music

Just a suggestion: NOS Mullards are typically the best sounding (according to most opinions) and longest lasting rectifiers, extant.                 Especially; those from the Blackburn plant.              ie: http://tctubes.com/Mullard-EZ90-6X4-tube-1.aspx     and:   https://www.tubemonger.com/Mullard_CV493_6X4_MINT_NOS_Blackburn_Gt_Britain_p/1212.htm          Don't know if there's much diff in sound quality/presentation, between the D and square getters, but given the low prices; I'd try both..

Tungsol and Valvo are excellent .

I have found NOS BRIMER 6x4 England EZ90 Black Glass Smoked Vacuum Tube as the best. I am using one in my Eastern Electric Avant preamp. It is a little pricey but worth it.