I used to own the cks77, gr07 and the ckm500, and I have auditioned the tf10 on occasions. The ckm500 is a nice phone for the price and can sound incredible after some eq, but it really is a step down from the gr07, or even the tf10. The cks77 was also just meh and no where close to the proficiency of the tf10. Both had somewhat similar sound sig though.
I would recommend the Ety hf5 but as others have said its fit is not for everyone and its best if you could try first. I believe it can be had for about 120 bucks online, representing great value. Gr07 is a great choice as well as it is very versatile and sounds good with almost anything, but there has been a recent price increase following the mk2 version introduction.
Below 100 bucks I would say the CKM500 is the best value for money as it does about 70 to 80% of what the gr07 or the hf5 does (in terms of sound quality only) while being much cheaper. But the other two are a definite step up though and its noticeable.
Just my 2 cents :-)