Since 90% of your time will be watching TV the center speaker will be of particular importance and I'd try to get the best one that fits your space and budget. Personally I like either using a monitor speaker (preferably matching the L/R speakers), but as this is not usually practical due to speaker height I'd choose a center with the tweeter located atop a dedicated midrange driver and then flanked by two midwoofs (I have been underwhelmed by center speakers that have two midwoofs flanking a single tweeter). Something like the Aperion Intimus 5C may be ideal as it comes in this configuration and is also less than 8" in height. Add their matching 5B bookshelves and an SVS PB1000 sub and you'd have the beginnings of a nice full-range system that's relatively economical and doesn't take up a lot of space. Paradigm also makes a Center1 speaker (and matching monitors) that would also fit your space and has a similar configuration, but at that price level I'd go with Aperion's silk dome tweeter over the Paradigm's metal dome, but that's personal preference. Given the size of your room I'm not sure I'd want to use tower speakers without a sub as they'd need to be pretty large to get bass near that of a subwoofer and may overwhelm your room visually and sonically.
As for electronics, an important consideration is the effectiveness of any room/speaker correction as that can make a big difference in what you ultimately hear especially in a smaller room. I'm not familiar with how the Oppo performs in this regard, but if it does well then maybe purchasing the Aperion speakers/SVS sub and the Emotiva amp mentioned above might make for an excellent combination for your situation/purposes (and I believe all offer nice in-home trial periods). If the Oppo doesn't do a good job with room correction it may be worth considering a decent AV receiver instead. Something like a Yamaha RXV475 should work perfectly fine for this application unless you want to spend considerably more for separates or a better AVR, but given this is mainly for lower volume TV watching I'm not sure it's worth the added expense. For whatever it's worth...
As for electronics, an important consideration is the effectiveness of any room/speaker correction as that can make a big difference in what you ultimately hear especially in a smaller room. I'm not familiar with how the Oppo performs in this regard, but if it does well then maybe purchasing the Aperion speakers/SVS sub and the Emotiva amp mentioned above might make for an excellent combination for your situation/purposes (and I believe all offer nice in-home trial periods). If the Oppo doesn't do a good job with room correction it may be worth considering a decent AV receiver instead. Something like a Yamaha RXV475 should work perfectly fine for this application unless you want to spend considerably more for separates or a better AVR, but given this is mainly for lower volume TV watching I'm not sure it's worth the added expense. For whatever it's worth...