[greenkiwi]

I'm going to have to find some local dealers with a wide selection.
 
The more I put headphones on, the more I find that I think I want to have velour ear pads (though maybe real leather is OK, never had a chance to have real leather ear pads) vinyl ones end up making my ears and head under the pads hot.
 
I am definitely up for cheaper options and the Mad Dogs look interesting too, I'll have to do some reading as I've not heard them before.  I already have some ANC headphones so I probably won't grab another pair.

 

[hipster2010]

The Shure SRH940 are great and have amazing detail. However the HD650s are considered dark, where the SRH940s are considered bright, which might not suit your preferences. Also, the headband is rather uncomfortable and would require some sort of mod to make it last for several hours of use. It does have velour pads though which is nice.

 

[Deep Funk]

Quote:

The Kenwood KH-K1000 is a good candidate. The mids on the HD650 sound more natural, but the Kenwoods retain the smooth and slightly dark sound signature the Senns are known for. A (unmodded) Sony CD1700 will get you even closer to the sound of the HD650, but unfortunately it is rare for them to turn up these days and usually when they do they've had the foam filter over the driver removed which results in a brighter sounding headphone.

I have a stock CD1700 out of use. Nice headphone if you like its sonic presentation...

 

[aleki]

I'll put down my vote for the FA-003/HM5/Jaycar.
Check out the pics 

 

[daveDerek]

Quote:

Kenwood KH K1000

Quote:

The Kenwood KH-K1000 is a good candidate. The mids on the HD650 sound more natural, but the Kenwoods retain the smooth and slightly dark sound signature the Senns are known for. A (unmodded) Sony CD1700 will get you even closer to the sound of the HD650, but unfortunately it is rare for them to turn up these days and usually when they do they've had the foam filter over the driver removed which results in a brighter sounding headphone.

 
let me third the idea that the kenwood is in the ballpark. does it sound just like a 650? no, but it has that general type of sound signature, plus it's pretty comfy and easy to drive. it's certainly worth a try.
for more info see:
 
- the main discussion thread:  http://www.head-fi.org/t/344543/kenwood-kh-k1000
 
- skylab's impressions:  http://www.head-fi.org/t/344543/kenwood-kh-k1000/150#post_4604463