I am also used to ordering online and since it's international orders for me calling is a lot more problematic (second language, time zone, etc.). Although ordering from them is a bit slower than just clicking some buttons on the computer, it's really not that difficult.
What you want seems to be that every part you might ever want will be available for comfortable online ordering and AFAIK this simply doesn't exist right now. So if I can do these international orders I'm sure you can do them much more easily inside USA.
AFAIK Ferree's prices for screws are not in their prixe list because they change a lot. Allied lists everything in their price list. I would like just call/email/fax once to ask for their catalogue and price lists (from both Ferree's and Allied) and then look there if they have what you want. Or you can download Ferree's catalogue which is online in PDF (if I remember they have their entire catalogue in PDF now, but not sure).
I think that specific type of screws you need I got some from Kraus, which not only doesn't have have online ordering, but sells only to "official" repairers/music stores/repair schools, doesn't accpet credit cards and has a $100 minimum for interntional orders... I don't think that particular screw is available from anywhere that allows online ordering, sorry.