...I would call Warren at ZenPro...let him know what specific applications you'll be using the PRE73 pres for and he'll explain the benefit of each mod...he's not a hard-sell guy...very sincere and trustworthy...he has actually recommended less expensive alternatives to me when he believes something in particular would better suit my needs...
...and as for the PRE73...great right out of the box!...but the modded variations do offer some advantages...either way, you will be impressed...great value...Bo at GAP is serious about developing very cost-effective products that really deliver value...I'm waiting on his new GAP compressor which is still being tweaked...
