Advise for new speakers for my basement exercise room


new member. I would  appreciate your expert advise for new speakers for my basement exercise room 15x25. Hard floor and walls with  4 windows and 9' ceiling. I am using near mint JBL 112s but hi frequency sounds are not realistic. Lows are great.  System is Nak CA7 pre, PA7 Nelson Pass 200w amp, and Sony ES707ESD CD player, AQ and Morrow cables.  Like upbeat music for exercise. Don't have time and do not want to go and audition and comfort level is about 5k or less.  My Mission 770s sound better than the JBLs there, but are needed elsewhere.
Thank you everyone for your advise and time.
johnmabaltimore
If you don't consider doing something to treat the room, you're setting off on a wild goose chase, in my opinion.
I’m thinking B&W would be the first place to look… with lots of room treatments and carefull setup. The room size is nice… but will need lots of deadening.. 
I use Spendors and a big REL sub in a mostly untreated basement. Sounds great and the highs are sweet.
Speaker sound is probably the most subjective ideal in the audiophile realm. If you like Mission 770s and the JBLs, then you seem to enjoy a deeper sound with a bass bias. 
My advise is to listen to a "brighter" speaker (B & W 603 s2 Anniversaries come to mind) and match them with a subwoofer that can be adjusted to fit your preferred sound signature for a 400 square foot room. A REL T/9x would give you the deep bass you crave while having the B & W's with their decoupled (37htz) tweeter and continuum mid-range provide a full spectrum sound. This set up with proper cables and wiring would be about $3,400.00. The B & W's also require solid power so that might require more investment.  I realize that may be beyond the budget of the OP, but a room that size, can easily cost $10,000 to fill it with proper sound. Test listen as many speakers as you can with and without a subwoofer accompaniment to hone in your preferred sound signature. Good luck.