Let's compare your new HT system to a new car, but let's make it really,really affordable.
I mean - it has four wheels, engine, breaks, you could fit (possibly) four (small) people, but you ever consider buying something like Tato Nano and what features it had to cut in order to be made and sold so cheaply:
https://en.wikipedia.org/wiki/Tata_Nano#Cost-cutting_features
What I suggest is forget about full sized new cars, your budget doesn't allow it, go with motorcycle or a used one.
If you go with regular (used) surround receiver and pair of nice bookshelf speakers - you could add good subwoofer and surround speakers later on.
If you go with ether of these system, it's very likely you won't be able to salvage anything should you want to upgrade it later.