Interested LED Replacement for 12V halogen lamps, only half luminosity compared with 20W halogen

I paid for a pack of ten in September 2013 just under 26 and found this to be very favorable. On the other hand, I would have wished that there would be a five-pack, because I really only needed five. Well what the hell I thought, so I have the same replacement on hand when the lights but not last as long as promised. The LED spotlight correspond in shape to the old halogen lamps and can also be easily installed.

However, there are some problems:
1: the luminance is significantly less than at 20W halogen lamps. The light color is, despite the name "warm white" still clearly led like bluish cool. I perönlich find it acceptable, but liked the significantly warmer color of the halogen light rather.
2: Due to the low power consumption possibly the old halogen transformer (which is in the field of instrumentation from 60-180W.) Below the intended performance range. Thus it is inefficient, can in some cases begin to hum and possibly go even prematurely broken. Remedied by a special LED transformer, the efficient, safe and permanent works at the expense of 10-20W. So a transformer costs about 20-30 euros, in which case even the question of whether to switch to a new LED lighting system does not prefer what is in terms of costs in similar regions.
I have left the old transformer and so far everything is working satisfactorily.
3: The LED Spotlight give a whirring / chirping noise from what you hear but only if you concentrate on it and is quite close. I take it while sitting on a sofa true unless it's absolutely quiet in the room, but it's no problem for me.

Summary:

- The light output is more comparable (which does not exist!) With 10W halogen spotlights,
o The light color is useful for LEDs but not stunning.
+ The look in on and off state in order
+ The beam angle is fine, the illumination quite evenly.
o Quiet twang, but very quiet
- Potentially problematic in old halogen transformers, in replacement of the transformers entail additional costs,
+ Durability until now after half a year perfectly. If the promised operating hours are correct, the price is great. In case of failures, I'll update the review.

Due to the poor light output, I can express a whole unfortunately no clear buy recommendation.

UPDATE after almost 1.5 years of operation (Jan 2015)

All radiators function remains good, and also the old transformer is still alive.