Personally, I would get the Eva. I was also considering buying a Trevi, but then I would be picky over which damier bag to carry. With the eva, its easier and its a clutch
Congrats on your speedy.Trevi PM is a beautiful bag.You can carry it on the arms or on the shoulder.It has both straps but it is on the heavy side (atleast according to me).But other than that, its a great bag.Eva is totally different.http://www.youtube.com/watch?v=It3IHhMUTGc reviews eva clutch.
SInce you have a speedy 30, for a variety in bag size, I'd get the Eva so you'll have a small bag for quick errands. I have the Trevi PM and it's a great size - it's very similar in capacity to the 30. I sold my damier speedy when I got the trevi PM.
I have a Damier speedy 30 that I love to use a lot and it is a largish bag. If you do not already own a smaller bag I would get a small bag next (the Eva) and then save up for the Trevi.
Thank you all for your suggestions! Looks like I'll probably get the Eva and wait on the Trevi as most of you suggested. I really like the versitility of the Eva and since most of my bags are rather large, it would be nice to have something smaller for a change.