I think it's quite difficult when faced with such a large range of technical specs and prices to find your optimum price/specification point. I've recently gone through this with the acquisition of a smart phone and it involved quite a bit of research and I now know an awful lot more about smart phones I did a few weeks ago! I also have paid considerably less than I could have done by acquiring a "status" phone.
The approach I took before acquiring my last tablet (and my circumstances sound a bit similar to your thinking) was to use an old military technique: analyse what you want to achieve/do and find the cheapest/optimal way of doing it. I found over the years with whatever I'm buying I start off at the lowest/cheapest spec and work my way up until I find something that is suitable – very rarely the cheapest or the most expensive.
Of course, until you start using the kit it's difficult to anticipate its shortcomings. As far as I can tell most tablets actually do the same but can perform/look better if you inject more cash (bit like cars – do you need a BMW 7 series to go Tesco shopping?). One of the things I found with the Kindle tablets is that they are really good value for money (especially if you buy them on a "cheap price" day) and do just about everything – that man Bezos ain't stupid. The standard price of a 7 inch is £50 and in my opinion is worth buying just as a tryout to see what you need: bigger screen/more memory/faster processor? If you're on the move, the bigger screen isn't necessarily advantageous if you couldn't put it in your pocket. When you've exhausted the possibilities of a 7 inch, it's always handy to have or you can hand it on to the kids.
The thing I've found with most technology is, that once I've identified the correct performance spec, I want it to be "nice" to use. Just like a car it can do everything you want except be enjoyable to drive. When I go away and want to trade with full facilities I use a Dell latitude laptop – good, solid, well performing, reliable: but you've still got to cart it around. When it comes to replacement I'll definitely be looking at the nimble & lightweight Surface laptop/tablet.
I'm probably suggesting what you've already worked out for yourself but it's always worth making a list on the back of a fag packet/envelope of your essential requirements and then starting from there. The one thing I've always found with sellers of technology is that they love to sell you more than you need.
:cheesy: