I'm in the same boat, looking for a keyboard. Tons of research on the web is one thing, but actually visiting and messing with a real unit is quite another. The spreadsheet idea is great. Here are some of the things I would compare:
On board amp wattage. Below $300 units typically have just 2 or 3 watts/channel; $300 to $500 units may have 5 or 6 watts per; digital pianos in the $600 to $1,500 range will have 20 to 30 per.
On board speakers - does it have separate tweeters?
Inputs/outputs: Does it have line in/out - stereo or mono?; usb connection for computer interface; midi; mike in; instrument in, etc. Which of these are important to you?
Number of keys: Many Casios provide a choice of 61 or 76 for $100 more, all other features being equal. Do you need 88? How portable do you want it to be? Don't forget, many units have octave shift which may reduce the need for maximum keyboard size.
Are the keys weighted or not. Weighted keys typically start with $600 plus units. Some people have said the WK7500 keys feel "semi-weighted" meaning they provide a bit more resistance than lesser models, but definitely not the feel of digital piano weighted keys.
How many voices does it have? Are they user modifiable?
How many rhythm patters? Are they modifiable
How many styles? Can you create and save your own?
Does it record? Can it record acoustic instruments as well as electric?
Does it provide training/learning aids? The great majority have metronomes and all provide for changes in pitch and tempo. Generally the least expensive ones, below $250 or so, provide the most learning aids. I guess when they begin to exceed the $300 or $400 level, they assume people can already play and they back off of providing learning tools. I think that is a mistake, at least for me.
What instrument sounds do you like best? Read reviews to see how instruments compare on those sounds. I like organ sounds, so the wk7500 and its baby brother, the 7000 excel in this. Some do a mediocre job with particular instruments. For example, I play clarinet and I think the less than $600 Casios are weak on this instrument.
As for places to test run keyboards, I was at first thinking I have to go find a big piano-organ store. There are none around where I live. I have to travel 15 or 25 miles to a larger town to find one. Definitely call first to find out what they carry. Also check Music and Arts type music stores. Music and Arts is part of the Musicians Friend/Woodwind Brasswind conglomerate. Their prices are the same as internet plus local sales tax. Local band instrument dealers often carry a variety of keyboards.
But even many small towns have guitar stores. And where you find guitars you'll find electric keyboards. I discovered such a shop just a few miles from my home. They have a great selection of Casios and their prices are competitive. That is where I will buy mine.
Good luck with your hunt. And if you are anything like me, a great deal of the fun is in the hunt. Drag out that process over weeks if you can stand the anticipation. You will most likely change your "features" preferences several times as you learn of the strengths and weakness of features sets in different models and different price points.
I started out before I did much research thinking I wanted an digital piano in the $800 to $1,500 price range. After looking at the features and going to a few stores, I learned that I don't need to spend more than $500 to get the combination of features that interest me the most at this point in my understanding. That is key: "This point in my understanding." My understanding may change next week. That's why I'm still researching. I decided I like a wide variety of tones, instruments and other features more than the refined, piano-like feel of a digital piano. Your top 3 or 4 priorities may be entirely different.
Connecticut is dense with urban places. I would be surprised if you didn't have 3 or 4 dealers within 10-15 miles of where you live.
Have fun in the hunt.
