Speaker(s) are a very important part of hearing what can be heard. Why have quality radio and antenna that are capable of bringing it to you if you can't hear whats there? Center speakers of a good build and purpose built externals are the way to go. Cheap is cheap, no two ways about it, unless its free. I gave less than $200 for my used SP-20 with DSP add on.
Heck, buy some used headphones (of decent quality), I have a set of AKG 518's that I still go to on occasion that I used before the SP-20. Headphones will get it done without a doubt. Just don't crank the volume knob on accident!
Draw back to headphones....not wireless in case of bladder duty when you don't want to walk away and might miss something. The SP-20 fills half the house with what I am listen to or waiting for.
I have had thoughts of dismantling the SP and taking measurements. I know a few people who are speaker box builders. Thing is...is it cost effective?