It looks like you have got a lot of things going on performance wise. CXPACKET waits (parallelism) should be addressed if > 5%. The IO waiting more that 15 sec indicates an IO subsystem bottleneck and the IO related waits seem to support this. However, that doesn't necessarily mean you need a faster IO subsystem, it could be a number of things including bad indexing, bad maintenance, or a big ad hoc query that needs tuning. Have you run any Performance Monitor Counter logs?
If I were in your shoes I'd start with addressing the CXPACKET waits by modifying Cost threshold for parallelism and Max Degree of Parallelism because that's a relatively easy one. Next I'd check index fragmentation and the last time statistics were updated. If there's no routine maintenance occurring, put it in place.
Next I'd run a PAL analysis, and go from there:
HTH,
Jon