The term 'burly' has been used above and that is probably a good quality to look for.
If you baulk at something because it doesn't look pretty enough then acknowledge that what you really want is engine bay jewelery and just go and buy that.
I still can't get my head round people asking good money for a strut brace that doesn't connect to the bulkhead. Then there are things with rose joints and other pivot devices that are just decoration.
Many engineering students do the balsa bridge competition at some stage. Here is an example.
http://www.garrettsbridges.com/videos/balsa-bridge-videos
This teaches them crucial lessons on how best to use material to get the best structural effectiveness.
My judgement would be that very few of the people who designed the strut braces generally offered for sale have done a balsa bridge competition or anything remotely like it. Not impressed.
Mark, it would be interesting to know more about the TUV standard. Standards can be misleading. ISO9000, for instance, can be a way of saying "When we f*ck up, we make a written record of f*cking up and we consider whether its OK to f*ck up and if we decide its OK to f*ck up, we write that down and then we just sell you cr4p anyway." One well-known American standard, often applied to electrical equipment, only tells you if the thing is likely to go on fire and not whether it actually works properly.