Infinite Product Options

Paid the fee for professional installation. These folks were in constant communication every step of the way, got the install done the very next day, and were very helpful when we requested a couple further tweaks.

I would recommend this app without hesitation. There are some negative reviews about the install cost, but If $20 to have a programmer come in and customize this otherwise free app to your site is too high a price then you may not be ready to run a business. You'll pay 10x that just to get a freelancer to pick up the phone.

Update 5/30/19:
Purchased the conditional login upgrade the minute it came out. This update is fantastic and free of game-breaking glitches that the competition suffers from. I would recommend this upgrade in a heartbeat!