A pretty good idea!
SR007 ... IMO
Huge price disparity between the two, I'd say 009 first and if it's "too much" sonically go for the 007.
You can likely narrow your choice by thinking about what kind of "sound" you like and what you plan to drive them with. They are finicky in different ways... The 009 not playing well with gear that's going to make it overly bright, and the 007 needing some go-go juice.
I find the SR-009 has more of an initial "wow factor," whereas the virtues of the SR-007 are more likely to creep up on you over time. Whereas I find the SR-009 fatiguing after a while, the 007 can give me hours of comfortable listening. Like @shipsupt said, they tend to pair better with different upstream gear.
Thanks for the tips guys - I managed to purchase a DIY BHSE so I'm leaning towards the SR007, but plan to audition both at my favourite store when work permits...
I must admit that I lend towards the modded HD650s over my modded HD800s, so maybe I'll be a SR007 fan...
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