Well the other guys will tell about the prices and SL models and stuff, but you ask about the cars itself right?
VTEC is a variable valve timing system and i-VTEC on new cars have both valve timing and lift variable. It was introduced first for high performance, but later used even for economy. There are many types, most common here being SOHC VTEC, VTEC-E etc. If you want economy, go for VTEC-E (E stands for economy) or high performance, DOHC VTEC though that's not too easy to find around here as I've experienced. i-VTEC on new Civics is totally different, it's a quite powerful car when driven normally, and uses VTEC to achieve fuel economy, if you drive it very calmly always below 3000rpm. It's the other way round than older Civics, where VTEC was used to increase power. That's why people here are complaining about bad fuel economy on the new Civics, as the Economy profile will nearly never get activated in SL. The car ECU monitors the driving conditions and activates economy when it 'feels' its appropriate, that is in highway mode. We don't have highways here = good power, less economy.
Ferio is a Japan model, made in 4 Door Sedan style. It's just a Civic that wasn't meant to go outside Japan brand new.
Vi-RS, a trim model in Civic, something like Base, Luxury, Sports or EX Saloon, SE Saloon on other cars. VI-RS is a sporty model in the Civic, usually with a very good engine. But after the start of the ES series cars in 2000, even that became a bit less sporty, as suspension was changed to cut costs.
Hope I cleared up something for you.