Using a pre-amp for HF really isn't of much help because you're mostly amplifying atmospheric noise.
Amplifiers are really only a substitute on HF for reasonable antennas.
I'm trying to think of some examples that might help you choose. The small AM/FM SW radios I think you're really limiting yourself.
I have an AOR scanner which has a BFO used for primitive form of SSB. While it works and it's better than the cheapy radios, it's still a notch below my HF radio.
I have a Yaesu FT767, which is a lot like the FRG8800 (or any other reasonable quality HF radio) and it's no comparison even the the AOR.
I have though of an example. If you tune between 7 and 8MHz
With the cheapy radio you might hear 3 high power AM stations.
With a scanner and BFO, you might hear about 8 stations.
With a HF radio like an FRG8800 you'll hear tens to hundreds of stations depending on the conditions.
And that's an ordinary HF radio, not one of the top shelf latest models
.
The best thing I can say is to test drive both kinds of radio. It's been a while since I visited Uncle Sam, but from memory you would probably be heading to one of the local electronics stores run by some nice gentlemen from some dubious middle east country.
Next you need to get your hands on the dial of a good HF or ham radio. There's a couple of ham radio shops in your part of the world. It really would be worth your while to visit them and ask them to give you a hand on demo of a HF receiver in action.
I did a quick search and this shop even mentions which hamfests they're going to be at. **broken link removed**
At hamfests you can play with many radios and compare them and get the best prices.
At the end of the day if you spend $100 on a cheapy and you decide that it isn't up to scratch, you might find it harder to sell.
The more expensive HF receivers hold their value quite well.
Even if you bought a general coverage RX HF ham radio and just used it for receive. If you ever decided to get a ham radio licence (which is easier if you listen to ham radio) then there's no need to spend anything to get on air.
The antenna impedance really doesn't concern you. While technically it makes a difference, to shortwave listeners a nice random long wire antennas do the job just fine.
The impedance of wire varies greatly with frequency so you'll go a bit nuts trying to tune it without a transmitter or an antenna analyser which will cost more than your radio.
Shop around. Go have a look at the good radios and get your fingers on the dial and get a demo.
Then go back to Habib's Supacheap Electronics and compare the $100 tranny.