Bapu,
If you have N20, you have a download right to the predecessor Nitro as well.
N20 is an upgrade from Nitro, but they are two different animals. Each unique and worthy having on the hard drive.
The envelope filer should be of keen interst for any guitarist. Has to be played almost like a secondary instrument, but if adjusted properly, gives the swell surrogate of a real tube amp pressed way over the RMS value. Swell sitar like response. Only other two units capable of this are AcmeBarGig Headcase and a recent freeware fuzz box. Unfortunately with my old age Altzheimers, can't remember what the other unit was. Will repost if the neurons reconnect and a moment of clarity happens.
Best,
John