As you said it depends on the priority of the listener. But it also depends on the frequency response of the surrounds. I find it non-immersive when someone has surrounds that desperately need to crossover to a sub at 80-120hz
and there is no sub there. Just half of a sound track with all the depth missing. It's a personal taste thing. I'd rather have 2.1 (or better yet 3.1) with all of the tactile feeling of a movie. If one must have some form of surrounds for movies then it's quite possible to get by with something cheap until you can afford really nice surrounds - they aren't doing that much work. I'm not advocating using garage sale speakers - just pointing out that whatever you have in the garage may get you by as movie surrounds until you can save for what you want, and will free up money for a good sub now. It's only when you get into 5.1 channel music with more than an applause track in the rear that a timbre match between mains and surrounds becomes a super big deal.
Again I'm not advocating that we all sell off our multi-hundred dollar surround speakers. I'm just pointing out that inexpensive surrounds can temporarily fill a sonic hole while freeing up money to fill another, to me, deeper hole (deep bass). In my case I'm using
$80/pr Wharfedale bipolar surrounds in my bedroom. They are filling that need just fine until I free up my dipolar Bostons for that job next month. Perhaps that's a good compromise for the OP. A good properly sized sub
and cheap surrounds for now. Next a timbre matched center, and then later when there is more money and no rush the OP can readdress the surrounds and move the cheap bipols into the bedroom
if he finds them lacking for the main theater room.
OP take a look at the above link. They may not sound like $400/pr surrounds but I suspect that they will get you by just fine until you decide to readdress the issue later. And quite frankly they may be all you need for years to come.