Webpivotable costs not much, works fine, but their design may be better, but thats just for me. Here their demo.
icCube – nice team, support, tool totally for OLAP and their webreporting tool is enough for some usual needs, but not more. Regarding futher detailisation, this is not for you.
Flexmonster – looks nice, works good, professional team and possible different types of customization, but quite costly.
Dundas is really not bad too, actually. You need to sign in to get their demo.
If you tell me more about your needs I’d try to be more specific. These apps were the first ones I remembered.
I have used and recommend Saiku.
It is a Pentaho plugin, you have to install it from Marketplace after you have installed and launched the Pentaho BI server.