More dumb questions from a noob. P7 vs HD650

[JHC76]

So, I picked up my P7s last week, and I do love them.  But, at this price point, I'm wondering if I should go with the HD650.  The HD650 are normally $500, but I can get them for the same $400 I spent on the P7.  At this time, I'm a few weeks away from being able to order an amp.  But, will I get decent unamped sound from them?  Is it worth getting these with the plan of getting a dac/amp in the near future?
 
For now, I will mostly be running through my laptop, but can drive them through my Pioneer Elite from time to time.  Is it recommended to get the best cans possible, then worry about upgrading?  Will I be disappointed in the sound?  I'm worried about the impedance difference.
 
As with most people, I just want to make sure I'm getting the best for my money.

 

[b0000]

Spend as much on headphones first before amplifiers and such. For the same amount of money, getting a better headphone will yield a significantly higher sound improvement than amp/dacs. So when do you get an amp/dac? IMO it's when you put on a headphone and think: "this is it. I don't think i'll be getting any other pairs".
 
I don't know about the p7, but you really can't go wrong with the sennheiser hd650 unless you're a treble freak. It's probably the most well respected headphone in this site.

 

[rubinstein]

P 7 has an impedance of 22 Ohms and efficiency or sensitivity of 111dB/V. It can be easily driven by a laptop or mobile device such as, ipod. However, a dac/amp would improve the sound quality. Most of the on board sound cards of the laptops do not offer good sound quality.
 
HD 650 has an impedance of 300 Ohms and sensitivity of 108 dB/V. It will be benefited by using a dac/amp. Laptop is not enough for bringing the best out of HD 650!
 
How much is your budget for a dac/amp?