hi
you can check out for either 2600XM model or 1800 model either with NM-4E model or NM-4ESW model.
If u only require ethernet ports then would suggest for 2600xm with NM-4E card.
2600 by default comes with one on board fasethernet so u can make use of that too connecting ur local lan.
if ur comfortable with fast etherswitch module then u can try out for 4 ESW module which can fit into 1800.
do check these links out for more info..
http://cisco.com/en/US/products/hw/routers/ps259/products_data_sheet0900aecd800fa5be.html
http://cisco.com/en/US/products/ps5853/products_data_sheet0900aecd8016bf0b.html
Note: inline with the etherswitch module just try a search over here in the netpro that will help u to get more info about that,also help to understand in configuring the same..
regds