Bass traps - foam cushiony items from Amazon ok?

Just walk around your room and clap your hands sharply. If you can hear the echo, you need a foam panel on ONE of the walls.

Yes, that's reasonable, but it's NOT bass trapping -- it's treatment for slap echo, which is much higher frequencies.

Foam is really not a good acoustic treatment.  Sure, it's cheap, but I have had weird results with foam.  The best acoustic panels are made from fiberglass strands or similar.  The cheapest of these are from GIK (or you can actually make them yourself from something like Owens 703 panels (just google for ATS Acoustics). 

For bass traps, you really need a very thick panel (like 12-14" or more).  Either that or tuned membrane bass traps such as the Scopus series from GIK Acoustics.  2-4" panels are not effective at bass frequencies.

Artnovion seems to have nice panels, a bit pricey. Much nicer looking than the lower priced items and hopefully much higher quality.

i just want to get a hint as to sound improvement by buying the cheap foam panels before spending big bucks.  I wasted alot by not going better in buying spkrs, upgrading speakers is a very costly path. 

No