boss looks like the one....but running 3 RC-300?
Three RC30 in sync would be perfect

I do not see any way to sync the RC-30 with anything else. What may seem like me being "nutters" (yes Ben, I know you were joking) is my knowledge of what is (typically) difficult to achieve with gear. Syncing things which have no provision for sync is much more difficult than unifying control over multiple devices which support MIDI.

Here is a solution which gives you unified control of four individual, synced loops (I apologize for my earlier mistake regarding the 45000's inputs):

1. Eventide Mixing Link, $299
2. Pigtronix Infinity Looper x2, $898
3. Pro Co 1 Foot MIDI Cable x2, $20
4. MIDI Solutions Thru, $40
5. Pro Co 10 Foot MIDI Cable, $15
6. Molten Voltage Tempode, $147
7. Pro Co 1 Foot MIDI Cable, $10
8. Behringer FCB1010 MIDI Foot Controller, $150

Shipped Total: $1,579

Compared to running an Eventide Mixing Link combined with a quartet of DigiTech JamMan Express XT loopers, unified control costs $880 (obviously, that price difference includes many features in addition to unified control). Since you do not need four tracks, that means unified control would cost you $980. This is what I meant by "diminishing returns."

By the way, the problem with the Boss RC-505 is that it does not give you independent control of the tracks.

...

The DL-4 is a good starting point, you even have an additional delay you can use with the looper. The Ditto X2 from TC Electronic would be my recommendation for starting out simply now, It has the same looping functions as the DL-4 (including half-speed and reverse) and is in stereo.

The TC Helicon Voicelive3 http://www.tc-helicon.com/en/products/voicelive-3/

Has separate Mic AND GTR In/Out (including a GTR Through that can go DI without FX) and Looping....
Claims to have TC Flashback/Hall Of Fame in it AND Looping.
You have to switch back and forth from Mic to GTR Mode but it looks pretty well laid out.

Researching...

So...

I won't know for sure how well it would work in practice until I hook a Stick up to one...

But you could connect the Bass or Melody Side up to the Mic input and run the other side into the Guitar input.
You would then have INDEPENDENT Multi FX and independent outputs for each side (Stereo) AND Synced Looping between them.

Downside is that the Vocal side has more vocal oriented effects on it but it does list some Overdrive/Amp algorithms on the vocal side as well as LOTS of Modulation, Delays etc that can all be time based and in SYNC with the Melody side.

They have 3 and 6 Button footswitch expanders that I am guessing allows you to control the Vocal and Guitar sides without switching modes back and forth.

Tom Greisgraber was on FHF a ways back, and I believe he spent some time discussing looping. I've seen him live, and given the level to which he takes it, it might be worth your time.

http://www.youtube.com/watch?v=B4wPqOVIJlU

What makes you think so? The input impedance is way too low on the Mic/Line input.

Why guess? From the Reference Manual, here is the list of controls which can be assigned to switches on either the Switch 3 or the Switch 6:

You would use a DI to connect to the mic input.
But until trying it, I wouldn't know if it would play nice.

I just got a Voicelive Play Electric used/cheap on eBay (for another use).
Will experiment

Yo rob, so you like those pigtronix looper? It looked like loop heaven, is it?