TOPIC: What switch can be a frame cloud?

Hallo there..
My name is Phil from the UK, just starting off on the CCNA journey.
I've got the Sybex book, doing netg at work and am building a home lab.
I've got a 2501 and a 2503 so far, crossover cables on the way from Ebay. What I'm asking is which switch is the minimum for a frame relay "cloud"?
Everyone recommends the 2520, with loads of serial ports. Why can't a simple 2/4 porter do instead? is it the dce/dte issue?
I'm not far into the training, so if I'm asking a dumb question, I'm sorry!