agree with BN regarding doing it yourself-
As a seller , I find that media companies do my head in - they are always trying to haggle, always trying to sweet talk you and I often end up just ignoring them half way thru a sale because they just can't cut to the chase, close the deal and show me the money! They might cost you potential ad spots due to trying to squeeze the max out of the client (oh believe me.. they always do.. max advertising for hte least budget - you pay the same and they keep the difference..)
Contacting the sellers directly (if this is an option) is definately better if you have the time - and I would imagine you will save money by making any haggled price your own (not splitting it with the media company). (my 0.10c)
More details please!