How loud are you wanting it? The Stealth bar you listed is going to flat out destroy any small portable bluetooth speaker. We're talking a $700 speaker set vs a $150 speaker.
You can go with a smaller Stealth and reduce your price and still be loud. And if it's near your head or aimed right at it, it's going to be quite loud. With a V8, bass will be minimal, but the bass addition can help balance out the highs in the speaker bar so your ears don't bleed.
If I'm going with my rig, and I take my tunes serious, I'm going with the full speaker bar. I've got an EU (or UE) Boom bluetooth speaker, and while loud, it's not going to deliver the sound that I want. I could easily hear it in my V8 CJ, but it's going to sound like what it is. A small portable speaker.
I run full speakers, and a sub in my rig. But I'm also full bodied.