Need to replace the mufflers

My '81 XJ650 had holes in the mufflers when I got it, but now one muffler has cracked completely in half. Can anyone recommend some good aftermarket mufflers? I'm not going for super-high performance, but I'm not looking for cheapo's either. I've looked at JC Whitney's and was wondering if anyone else had used them.
As to actually replacing the mufflers, it seems I have to unclamp the pipes from what is a 4 way manifold under the engine. The manifold seems to split left and right off the bike, and then the mufflers have to be cut off the manifold. There is also a chrome heat shield clamped on the front of the manifold, and welded on at the back. It seems like it's in the way of where I need to be doing my cutting. If I remove it, I'm afraid I won't be able to re-attach it.
If anyone can give me some pointers about the whole procedure, I'd greatly appreciate it.

 

No cutting is necessary to remove the mufflers. There are bolts on the end of the mufflers where they clamp on to the collector (the 4 way to 2 way manifold that is under the engine).

 

Here's a close up picture of the under-side where the muffler meets the back of the collector. There are no clamps that I can see, just what appears to be a weld seam. Or does the muffler inlet just slip inside the back of the collector? This setup seems o be different from the diagram in my Haynes repair book, which shows the mufflers being clamped on.

 

On the 650 Maxims, there sure is. Your Seca has a collector-box system; not all XJs are so-equipped.

The early Maxims had a "crossover" system with the mufflers welded on. To replace just the mufflers on those bikes, they do need to be cut off. I believe the usual "fix" is to weld a stub pipe in, then clamp the replacement muffler to it.

 

So it seems my bike probably is an older model. The collector does have a crossover pipe under the motor, connecting the left and right sides behind where each set of two exhaust pipes bolt on and are merged into one pipe.

 

That's a weep hole, to let water drain out, no worries man.

 

That little hole was never the problem. The holes I was referring to are over an inch across half way along the pipe. What my photo doesn't show is just to the right the muffler broke completely in half.

 

Oh. Yeah that's a problem