are all wireless headphones rubbish ?

[movingtables]

I got some Sony wireless headphones for xmas £40.
and im not to impressed when using them with the xbox360 from my amp.
Bomb just dont sound good anymore in call of duty 4 lol.

before i send them back and spend a bit more, i was interested to know if
i am wasting money with wireless and should stick to corded?
im not a sound fanatic but the sony's just didnt cut it.

below are the ones i am now looking at:

Sennheiser RS 140 Headphones £89.99 delivered.



So what do you guys think ?

SPECS:

Max. Sound Pressure Level: 110 dB
Powering: 9V DC (transmitter)
AAA batteries (receiver)
Weight (Transmitter): 430 g (incl. audio cable)
Weight (Receiver): 280 g (incl. batteries)
Range: bis zu 150 m (for 926 MHz up to 100 m)
Modulation: FM Stereo
Signal-to-noise Ratio: > 68 dBA
RF Frequency Range: 863 ... 865 MHz or 926 ... 928MHz
Dimensions (Transmitter): 85 x 225 x 133 mm
Frequency Response (Headphones): 18.....21000 Hz
Transducer Principle: Dynamic, closed
Operating Time: 20-25 h
Total Harmonic Distortion THD: < 0,5 %
Jack Plug: 3,5mm / 6,3 mm stereo (863-865 MHz), cinch (926-928 MHz)