SSRS in existing 2010 farm

Hi

Is it possible to enable SSRS within our current SP2010 Server farm? I have seen numerous doco, but all are pointing to the fact the I need an additional server which I then need to integrate into the farm as a WFE.

I currently have a 2xWFE, 3xApp and 1xDB server setup and would like to run ssrs within the environment, not have to create an additional server, and thereby have to pay for another sql licence.

I have not found any doco to date that explains whether this is possible.

I am running 2008R2, SQL Ent, SP2010 Sp1, with a service account that has DBO access to the reportserver (and RStemp) DB's.

Doco I have read is:

http://msdn.microsoft.com/en-us/library/bb326356.aspx

http://technet.microsoft.com/en-us/library/bb677365

http://technet.microsoft.com/en-us/library/aa905869(v=sql.105).aspx

http://msdn.microsoft.com/en-us/library/hh479775.aspx

none of these refer to getting ssrs working within a farm, rather than adding it into a farm.

Any help most gratefully appreciated.