Hi Fishy... I'm a noob also in headphone world, so my advice might not reliable. I'm sure that many headfiers in this forum will able to give you more accurate advice. I'm owned DT231 as my first cans, and overall, I like them. I have never heard HD25sp personally, but I heard that they have a lot of bass and I think more than DT231. However I think the bass in DT231 is already good enaugh for me, and this is the reason why I choose this one instead of choosing HD497 and px100. I like to use this cans for listening instruments, or pop but for rock, I think sr60 is better eventhough it is an very open cans. DT231 do leak a lot considering it is a closed phone, but if you compare to open cans, it still better in terms of isolating especially from grados. One thing that I like about DT231 is it is very comfortable so that I can use it for hours...but it is will depends on your head and ear size of course. Personally, for the money I've paid for this phone which is 30 pounds (which is the same price for ipod bud), maybe I can say that this is one of the best value cans, better than other cans with similar price (HD25sp here cost 80pounds). If you have a chance to demo them, that would be the best way, you can choose which one is the best for you, coz every opinion hear is a matter of personal taste. I can find some headfiers who consider DT231 is a nice budget phone, and some headfiers prefer HD25sp instead of DT231. Well I think for a noob like me, DT231 is a good entry level cans for my first step in headphones world (and also for the money, it doesn't make me broke, I can still spare some cash to buy DIY amp) but if I have more money, and wants something better, I won't buy HD25sp but I will buy HD25-1 instead, I think from the review, they are much superior compare to HD25sp, or since I like beyer, maybe I will upgrade to DT531 level at least.