Reddit reviews Miccus Mini-Jack TX - Bluetooth Transmitter, Ideal for Adding Wireless Audio to iPod, Kindle, PC, DVD and More. Does NOT Pair with Phones or Tablets (Single-Link)

Just get an adapter like this.

Who needs a new head unit? https://amzn.com/B002HHLOWC
And seriously? You're worried about audio quality in the car? Where your baseline is directly linked to speed?
I certainly didn't notice any difference. I wired in one of the receivers linked behind my old stereo and just forgot about it. Less wires on the dash. Less dinking with the plug being all clapped out in my factory head unit.

After many years of buying headsets I finally found the best setup that is so comfortable for extended play.

First you will need one of these splitters possibly. I also like this cord extender.

And buy following:

• Decent headset. I personally like earbuds, they are just the most comfortable, period. I've spent hundreds and hundreds of dollars on earbuds over the years and honestly, price, performance and comfort (at least for me) these are my favorite. They sound better than much more expensive headphones I've used.
  
  
• Standalone mic. These are cheap, this way you can pick the right kind of headset for your comfort without having to compromise for only the ones with a microphone. And trust me I've used a lot of the combo deals over the years, but my last straw was a pair or Sennheiser headphones+mic combo that were just so uncomfortable I couldn't wear them for longer than 45 minutes. Worst part was they were expensive ($300) and they didn't even sound that good.
  
  
• Bluetooth transmitter. This is what I have.
  
  
• Bluetooth headset
  
  Now the range is not that great ~10 yards or so (trough a wall), I could probably get a better range with a different headset/transceiver combo but that's what I use, and it works fine for me (I do wish the range was a tad bit better).
  
  When I step out to my kitchen (porch to smoke) to make me a drink I just put my bluetooth headset on. No hastles with battery because when I come back to my computer I just put my regular headsets on and plug in my bluetooth headset to charge.
  
  Total cost $140. (including a $10 standalone microphone)

If I understand your situation maybe this would be an option in the output of your belt pack.

http://www.amazon.com/Miccus-Mini-jack-Transmitter-Headphones-Receivers/dp/B002HHLOWC

Check the reviews it has on other sites; if they're mostly good reviews, then you might have received a faulty pair.
I went on Amazon and did a quick search, adding in a filter for only things with 4-star reviews and up. I see some seemingly-good Sony and Sennheiser ones for $60-$90. I wouldn't go for anything less than $40-$50 unless you really trust the brand or know for sure that it's good.

Alternatively, you could get something like this and plug it into your TV, and it'll let you use any set of wireless bluetooth headphones.

I'd say no, but there are products out there that do what you want.

This looks like it would do what you want.

Out of interest what are you wanting to broadcast from that doesn't have a bluetooth transmitter built in?

would
Bluetooth work better?
Transmitter
http://www.amazon.com/Miccus-BluBridge-mini-jack-Transmitter-Headphones/dp/B002HHLOWC
Receiver
http://www.dealextreme.com/p/mini-rechargeable-bluetooth-v2-0-a2dp-audio-receiver-67666

https://www.amazon.com/Miccus-Mini-jack-Bluetooth-transmitter-headphones/dp/B002HHLOWC

http://www.amazon.com/Miccus-Mini-jack-Transmitter-Headphones-Receivers/dp/B002HHLOWC

You have a bunch of options for this actually. This is the first result I saw. Is this what you were looking to do?