Personally, i haven't heard the PS200s but i am assuming that they should sound alot better than the CK7 (going by Phiaton's pretty excellent track record so far).
Firstly, we have to remember that CK7 is a very old design and it was released circa late 2005.
That was a period of time when the earbud scene was pretty dead, the only promising products in the earbud scene were AT's own cm7, cm700, Sony's e888
and a new relatively unknown earbud called the PK1 produced by a chinese company called Yuin.
On the IEM side of things, BAs were just starting to pick up momentum.
Etymotic being around for the longest time was a natural choice for most people wanting serious sound, Shure had just started about a year ago with its E2c, E3c. The first dual BA E4c flagship was just released. Even the E500s were not out then. Westone's own um1 was still months away from release.... You get the picture.
When CK7 came onto the scene with it's exotic titanium housing and 11mm dynamic drivers (most dynamics at the time were 9mm and below),
it was a breathe of fresh air.
Alas, 5 years + is a long time for any IEM to be on the market, and the quality that dynamic IEMs are putting out these days really do surpass the SQ of the CK7.
However, if you're looking for a casual commuting IEM and don't mind a V-shaped frequency response,
CK7 is still one of the best isolating dynamic IEM around.
Quality and attention to detail in its price range is still outstanding by today's standard.
So, in the end, it boils down to what your needs are.
I have taken some pics of my CK7 (mine's the much later version which is dark nikel plated) next to my CK100, hope it helps.
CK100 (left), CK7 (right)
Cable of CK7 has a slight rubbery feel to it like the CK100. CK7's cable is of good quality and is not prone to memory effect or microphonics. Chin slider is a simple plastic tube affair like the CK100 but it serves it purpose fine.
CK100 (left), CK7 (right)
Strain relief on exit to housing is softer and thus better on CK7 than it is on CK100. Notice how the words ATH-CK7 and Japan are embossed on the bezel sorrounding the nozzle. Very nice attention to detail in my opinion.
CK7 by itself
UE single flange tips work best to bring out the recessed vocals on my CK7.