Well, the difference between the Quattro and the Sovereign is pretty much the tech of it. The Sovereign is a BBS machine...Broad Band Spectrum, which means 17 frequencies. And it's quite the machine. Multiple tones, iron masking, deep seeking...awesome beach machine. The only visual is a meter that gives you a conductivity reading realative to your target to go along with the tone...it's 0 to 550 and a quarter would be at the top of that scale. They are killer beach machines too and great on land as well. There are no "programs", just Disc and Notch control and sensitivity. Like the Quattro, it's a threshold machine, meaning it hunts with a slight background hum that breaks when you hit a target and the target tone takes over. It's a very capable machine. I've found many gold rings with mine at the beach and a lot of silver coins, bullets, buttons, etc. on the land. A new Sovereign Elite will set you back about $600.
The Quattro is a different animal...more hi tech than the Elite, it has a digital screen, is a Full Band Spectrum (FBS) machine with 28 frequencies, like the Explorer is. It has 4 preset programs...Coin, Coin/Jewelry, Relic, and All Metal. The program you choose determines how far down the scale you want to go as far as pulltabs, foil, and other non-coin items...which would include your gold rings. It's a very powerful machine and has great depth and sensitivity to small items. Either one would be a great choice. Either one is easy to learn and use, truth told the Quattro is probably a little easier and more fun. So if money isn't an object, go for that one. Hope that helps.