Congrats mate, you just got yourself an awesome amp!
Tweaking a Recto is a bit confusing at first, since the EQ section of the amp is very powerfull, thus enabling a huge variety of tones.
I think the cab has a lot to do with the bad tone, since as far as I know, it was designed for modelling amps.
Some tips:
-don't overdo the gain, I personally never go past 11o'clock on modern mode.(it might sound weird at first, but you'll get used to it)
-remember that the presence control on the red channel is super aggressive, be careful with it.
-the Recto EQ is a bit confusing at first, and you really should EQ with your ears, not your eyes. For example, the old "more mids, more mids" doesen't necessarily sound all that good. I am not a scooper, but with the Recto I usually have the mids at 8:30 and then I bring back the mids by dialing in a lot of presence, which brings a lot of high mids to the tone.(at least on the modern mode)
-use moderate EQ settings! Below 12o'clock is usually fine.
-boost that biatch! A Tubescreamer/OD-pedal with the gain on 0 and tone/level the way you want will make the amp sound more focused.
-pick hard! The Recto sounds killer when you really beat the s*** out of the strings.
Of course, those are just tips and in the end it all comes down to personal preferences. These are just some things I have learned when tweaking my Triple Recto.
And because this is the Andy Sneap forum, you will propably bump into the Sneap Recto settings. These settings were used on an old 2channel Recto/red channel which has a darker tone when compared to the red channel on a 3channel head. So if you want to use the Sneap settings on your 3channel head, use the orange channel, because it sounds a lot more like the red channel on a 2channel head.
Have fun, and don't give up