Dual Purpose breeds

[VictoriaTemple]

I would definitely go with Marans. Their eggs can't be beat and they stay tender after growing out (so I'm told). Maybe you could cross with your Welsummers, see if something interesting results...

 

[Amer]

I love my Buckeyes, and would especially recommend them for northern climates. It is also nice that they have clean legs, making an overall low maintenance bird. They go broody occasionally and lay into the winter. They are actually faster in growth than the Red, which is more for eggs.
(A Buckeye cock will weigh 9 pounds while a RIR weighs 8.)
However, unless you get a Buckeye from a reputable breeder, they will not have the growth that you want.
If you order from a hatchery, most dual purpose breeds have similarily poor carcasses.
I have also found that out of all Buckeye cocks I have owned, I have not met an aggressive male. They tend to be respectful, though they take the leading position in a mixed flock, while the hens are mild and inquisitive. I can not say that for some of the other dual purpose roosters I have owned.

Buckeyes are not the only choice. If you live in a southern state you may choose a single combed breed, (though most Buckeye breeders I know live down south) or you might want something with fancy eggs like a Marans.
That is just my choice.