I unfortunately do not have any affordable Hifi stores near me, they mostly sell really high end stuff. I am curious about not needing a sub out on an amp, could you explain?
Firstly, the Marantz I mentioned and lots of other modern amps have pre out/sub out. this is the simplest option.
As to if you need a sub, you will only know after listening. I have two separate setups in my living room. despite relatively small speakers I have never had the need for a sub. I do use a sub on my AV system.
Best advice, start with speakers and an amp then decide if you need a sub.
There are multiple ways of connecting a sub without a pre out. The two simplest, and probably most appropriate for you:
If you had a pre out, you would run a single RCA coaxial cable to the low output on the sub. If you don't have a pre out on the amp, you run speaker cables from the amps speaker binging posts to an RCA Y adaptor, that will then run an RCA to the sub.
If you your sub has a "high level input" you can run the speaker cables directly from the ap to the sub (some high end experts recommend this even if you have a sub out).
In both the above cases you can "piggyback" the binging posts going to your regular speakers, or use a second set of outputs if the amp has them (common on Marantz amps).
For more advice and technical information just google something like "subwoofer without sub out", there will be lots of information.
You mention stores near you are mostly high end, where are you?