What I'd suggest you do is get a Pioneer 1015 and a SVS PB10 for about $1000 total shipped. If the increase in bass isn't amazing I don't know what else you could do.
That is a wierd dilema you are facing there with regards to the bass from the Marantz. I have to admit that I'm a little upset with the limited crossovers my Marantz provides, but when set to large my speakers get the full spectrum of sound. I usually just go with a crossover of 80hz (the lowest seting on my receiver) and let the sub round out the rest.
Spiffyfast has a good idea about going with the 7400 if you wish to stay with Marantz. Outlaw will be out of your price range for $1000 and you'd be stretching getting Nad gear for that price as well. I love Nad equipment but it is a bit pricey for me right now. The Denons you are worried about being too bright have great eq's that will let you tweak different settings. I have a Marantz 8400 that retailed for about $1200 US, I installed someone's Denon 1905 for them on Tuesday and it has more features than my 8400 with a retail of about $500 CDN! after taxes. Now it isn't as powerful or as well built or as sexy and it doesn't have as much "snob appeal" but it is one heck of a little receiver. The 3805 is available right now for $1000 on the nose at crutchfield and would do everything you want and more.
If I was you I'd consider the Pioneer 1015 with the sub or the Denon 3805 without it. They will both outperform what you are using now to a huge degree. Good luck with your purchase.