RFID Readers Arduino

I wasn't sure exactly which forum is the appropriate place for this question, so here goes:

I'm working on a project that will be using two USB RFID sensors, attached to a microcontroller (or two, if we were to use Arduino) which can run a program that will detect RFID tags as they pass over the sensors. Basically, we need a board that will be able to maintain a sampling rate of at least a few samples/second on both readers. It will be run for 8 hours a day, 5-6 days a week, for a four month period, and it should be as simple as "turning it on" in the morning and "turning it off" in the evening (once it has been completely set up, of course).

We're currently looking for a good, inexpensive microcontroller which can meet these "specifications" (vague as they are). Will Arduino work for this? What considerations should we take into account? Any advice would be greatly appreciated. :)

Beyond reading the tags, what do you expect the micro-controller to do? The Arduino is capable of reading multiple RFID tags per second, and doing something based on whether the tag is valid, or not, if the number of valid tags is small. Determining if a tag is valid, when there are 840,000 valid tags wouldn't be possible.

I'm working on a project that will be using two USB RFID sensors

One "consideration" is that the Arduino can't use USB sensors: both are "slaves" that must be controlled by a USB "master" like a PC.

You'll want a reader with some other interface, probably serial. If you go with a serial reader, you may want to use an Arduino Mega, which has 4 hardware serial interfaces, to simplify communications (since one serial is usually used to talk to the PC).

Most commercially used RFID readers I know of use a serial interface (Wiegand). All you do is have them read until they get a valid card, after which it is up to you to decide what to do with the data.
If you need realtime validation with a large nr of cards, your best bet would be to pass the data to a PC capable of running a database and crunch the numbers there.