Yes, you can use Auctiva to create listings for your ebay store and you still enjoy all the benefits like schedulings listings in advance.
There are several threads that discuss the store fee hikes that go into effect tomorrow. I will try and find some for you if you are not already aware. Many are closing their stores and many are staying..I am hanging on for a couple of months to so how things go.
Stores with really low priced items will be alot harder to be profitable so it also depends on what you are selling. I know many sellers with hundreds or thousands of items are closing shop as it will costs too much to just have a store. We use to say that you have to have at least 100 items in your store to make it worthwhile and I am not sure if that number is changing but it is a good mark (I have yet to achieve just because of the lack of time with twin 3 year olds.
But I hope to get there soon for this Christmas season.)Please feel free to come back and ask any more questions you might have, we are all here to help!
Marcia