fgoldberg,
There are many variables to the bloom time of bulbs and bulb species but in general here are the bloom times of the species you listed:
- Scilla - Common name - English Bluebells, zones 5-8, bloom time late spring

- Ipheion - Common name - Spring Starflower, zones 5-10, bloom time midspring

- Chiodoxa - Common name - Glory of the snow, zones 3-9, bloom time early spring

Hope this helps. I have found some really good information at the website below and a pretty good newsletter that covers a little bit of everything. I have found that you can also ask questions from a professional.

Here is a link that might be useful: Garden Resource