Hi,
Recently I was looking for a replacement of my broken RB450G and trying to find a solution that has enough gigabit ethernet ports and a miniPCI slot for a WiFi add-on card. I found the RB493G which is a little bit expensive and the 9 ethernet ports are too much for a small network (like mine). It would be good if MikroTik produced an RB450G like board with 5 gigabit ethernet ports with a miniPCI slot (e.g. RB451G). Is that possible if MT will make a board like this in the near future?
what about RB751G, however it has integrated radio.
I saw that and it looks much weaker than RB450G (slower CPU, slower switch throughput) and I’m not sure if it can handle my 80 Mbps PPPoE WAN connection. In addition I have a few PCs connected with Gbit that put large amount of data through the network.
we have not tested exactly that, but you can try. After all it has around 370Mbps throughput with firewall/conntrack and routing
swtich is wirespeed.
And how much is the speed drop if I use queue trees (+many firewall mangle rules) for QoS purposes?
if you have RB450G still in place, you can try by reducing cpu speed to 400MHz that will be the same as RB7501G regarding speed.
I just measured it and at about 60 Mbps the CPU load was 100% and about the half of this usage was queuing so this CPU speed is simply not enough for such bandwidth. 
there is always a question - is your queueing optimally configured?
Also, you can wait when RB2011 with wireless comes out.
RB2011 with wireless… more info on that please … (try concentrating on when) 
will there also be pa minipci slot version or just integrated wireless… Also any more RB2011 improvements like more memory or different chasis options? As I wrote to your sales guys, 10" rack chasis would be nice for any rb product - no such router/switch at the time.
cannot comment on when part, however there will be rack-mountable cases from MikroTik for RB2011.
For announced products - wireless is integrated.