I use an excelsior 940. I have the Solton MS40 a predesessor to the sd2. It's quite a large gadget but has loads of wonderful sounds and styles. Works well with a couple of pedals. At the other end of the scale is the brand new Limex desktop. Fabulous new module developed for accordions. it's 1/3 of the size but pricey. Limex also do an internal soundcard, where no exterior module is needed. All sounds & styles are accessed by a small monitor that sits on the end of your accordion. you can even download MP3 backing tracks into this machine. Wonderful !! Again, it's pricey, but the sounds are marvellous. There's also the other module I use which is a Roland MT32, small, with no rhythms, but some fairly good sounds. Nice piano for left hand work. My advice is to use something that other players use, some modules don't work well with accordions. I've found that out to my cost years ago.