CBSubs with Community Builder should be suiting your needs as i understand them, with following exception from your text above: It is not a cart, so you cannot change number of merchandises (e.g. your gif-cards) bought before checkout, but can buy one merchandise at a time (or define multiple merchandises for different quantities of cards/gifts.
Btw, It has never been our intention to withhold any information on CBSubs, but it has been always our intent to give information in an overlookable concise manner so that people don't have to go through a never ending page of features, so I would really love to know what gives you that impression of "withholding", and which informations you were looking for and didn't find.
And CBSubs comes at no risk with a 30-days money back warranty, so why not just get it and try it out ?
it will be much easier to see it in action on your own test-site in your own environment, and will answer many of your questions. Plus we are here to help you if needed (see Support main menu, and tabs, incl. Services for personalized services)