Garageband is an exact clone of Acid. Acis is for PC and I use daily. Acid Pro 6 has everything you need now (multitack, midi, punch in and out) and the learning curve is nominal. My number one suggestion for you (especially if you're using Garagaband as a jump off point)

you can get a free demo of acid on their website, you can give him a shot and see what he thinks. You'll also get some free samples for it :wink: