That's actually a good question so I'll jump into it.
The Dual Rectifier was the original of the Rectifier series until the Triple Rectifier came out somewhere around Revision F of the 2 channel models. The original thought was that it had two types of rectifiers, tubes and diodes. That was laid to waist when the Triple came out having 3 rectifier tubes and also silicone diodes. Some time later (I'm not sure when) the Single was released as a 50 watt head that had NO rectifier tubes. It only ran on solid state rectification. Also it ditched the Spongy/Bold switch as well. So the meaning between Single, Dual and Triple really hasn't been consistent from one head to the other, save for sounding good with the name. I don't know why it wasn't designed with at least one rectifier tube in mind, but hey, that's not for me to decide. A large part of the Recto sound is from that pre-amp combined with their cooly biased power section, and the Single still had that. The rectification type does have an effect on tone; it's not super pronounced but it's there. Diodes are more aggressive and upfront. Using the rectifier tubes introduces a little sag into the sound and gives it a slightly more loose, vintage vibe.
Like it's bigger brothers, the Single Rectifier underwent a revision. Series One accepted only 6L6 tubes and featured 4 modes total: Clean and Pushed on Channel One and Vintage and Modern Channel Two. Series Two brought about the adjustable bias switch to run EL34s (which sound FANTASTIC in a Single Rec) as well as introducing Raw mode to the gain channel. Two channel layout on both versions with both Output and Solo controls. It also got a sibling called the Recto-verb: Basically the single recto with reverb. Still a fairly sought after little amp too. People that have their Recto-verbs love them. Great flavors of Recto tone that unfortunately were discontinued recently since the newer Multi-watt Rectos can switch down to 50 watts. Still, if you're looking for good Recto tone on the cheap, these can be had used for a great price.
Mini Recto - 25 watt amp switchable to 10 watts. Recto preamp with EL84 power section. A little brighter I believe than the standard Dual and Triples. This is most likely due to the EL84 tubes vs 6L6s that the bigger Rectos ship with.
Speakers are very, very subjective, especially with Rectos. I am one who LOVES the Recto sound through a Mesa cab with Vintage 30s. I also love a Mark through those speakers and 5150s through them too. But V30s are not for every one. A lot of people have had great success with various cabs and speaker combos. Mills makes phenomenal cabs. Avatar makes a great cab for the buck that you can get loaded with whatever you want. Mojo tone as well. Genz-benz cabs sound good too. The Revision G Dual Recto I just got? I played that through a Genz-benz with Swamp Thangs to test it and man that was a hellaciously awesome sludge/doom tone coming out of it. Celestion and Eminence both have a variety that are great. Legend V12s fit the less aggressive/shrill (whatever you want to call it) bill of the V30 as do WGS Veteran 30s. I've heard them run through G12T75s that have sounded good, despite that speaker being scooped in the mids. G12K100s are another favorite for Rectos. EVs too, but they weigh a ton and cost a ton, but if that's what you want go for it. MC90s (Mesa Black Shadows) also sound fantastic. A more even response than the mid heavy V30 (and sounds great mixed with V30s). What I'm saying is this: different speakers will profoundly affect the voice of this amp as will the construction of the cab it's in. If you can try one with different cab/speaker combos then do it. It'll help narrow down what you want for your tone.
Hope this helps dude.
