The Rio is smaller than the Spectra, but either can be had with the features you list for a price.
ALL Kia's have the same warranty, which overall is very good although there are a few cracks an owner with a problem can fall into if he or she isn't wary. Just read and understand the fine print.
The AC components are virtually identical on both vehicles, and frankly since you are buying a new vehicle from a dealer if the AC didn't work well then I wouldn't buy it!
As for purchasing advice, nothing beats having all the information. Try web sites like
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(Kelly Blue Book) or
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or other similar sites that will give you list and invoice prices, although the term "Invoice Price" doesn't really tell you what the dealer paid - that is called "Dealer Net", but it is a good place to start bargaining from. Businesses like Sam's Club and Costco offer no-haggle pricing with participating dealers for around $200-300 over invoice price. That's how we bought my wife's Sorento.
Above all, don't be afraid to say No and walk away. And understand that the deal they are offering you isn't really "for today only" or "take it or leave it" - you can still come back in a week and they will be just as glad to sell you the same car for the same price they quoted last week. In fact, if you walk out and the salesgoober is motivated, he'll be on the phone with you in a day offering you something to sweeten the deal.
Cheers - Jonathan