Speaker jumpers

No

jumpers without replacing the internal wiring will do nothing

jumpers and replacing the internal wiring will do little 

non 'wimpy' is only needed if you are moving a lot of current - even current hungry magneplanars need only banana connectors for adequate flow at the highest SPLs

if you have a need to tweek work on room treatments

Whimpy?  I think the ones that came with my 804s look and work great.

I heard a definite difference when I replaced the stock jumpers on my Harbeths with Audience AU24 jumpers.  In my case, it cleaned up and defined the bass much better.  But in a different room or with a leaner amp, the stock jumpers may have worked better.  So the answer is - aftermarket jumpers may sound different, but are they better?   That's what listening is for.  It's got to be in your home with your system if you really want to get it right. 

Room treatments were probably the best upgrade I've made.Its just in this hobby it's hard to get away from more is better!

I have the B@W Martrix 800 I replaced all of the stock jumpers (3 sets per speaker)  with High Fidelity level 2 jumpers and improved the sound greatly. Before that i changed the stock jumpers for some older Transparent Ref. XL jumpers and only in the mid and tweeter did i get a small bump improvement. But with the High Fidelity level 2 jumpers it was a very good improvement across the board. Base was tighter mids and highs where much more detail, but relaxed sounding no hard edge.
Room treatments are a big plus too.
enjoy Pete