The ”sweetspot” in the Nordost line of cables

Find a dealer that can loan you the dealer demo cables.

I have demoed Odin II to Blue Heaven in my setup. 

With my level of setup-H2 from the wall to speakers. 

Personal cable reviews are just that, and not what you may experience. In some locations, it may not make a noticeable difference at all-my subs are plumbed with Blue Heaven-just because.

Questionable value at MSRP. If you can find used for 1/2 or less, great cable. One thing for certain- they make your setup look "high end" to your non audio friends.

"Would Shunyata Alpha be a better match than the Nordost Leif cables?"

Your ears should be the only one to tell you that, certainly not anyone here.

Only the power cable incorporates construction principles of the upper levels. That said, it is a good buy to find out if Nordost catches your ear.

Heimdall is entry to the Nordost magic.

Your amp is at a level that shouldn't be dependent on cable brand. The "signature" should already be on display with your existing choices.