Originally Posted by lgtg
or is a smaller volume more appropriate?
No, a quart is perfect. I typically use 2L starters for my 5-gallon batches. Now, if you were to use a 2L starter for a 2.5gal batch, the problem begins to arise: your starter volume (which is presumably extract) begins to substantially influence the overall volume of wort, thus possibly drastically changing the character of the beer. But one quart would be fine.