Are marantz power amps any good?

Are there lesser amps decent for stepping  up into seperates for the first time ?

Sure, but not from Marantz.  All their other power amps are HT amps that are made in China, fairly low powered and IMO, less than desirable for true HiFi.

Why do you need 300 wpc like the MA9s2's anyway?  What exactly are you trying to accomplish with your system?

I don't need 300 watts per channel I'm just stepping up into seperates or intergrated , music quality is huge , just wanted to know if the marantz amps would be a good start on the lower budget side 

In the mid to late 90s, I had the pleasure of owning 4ea of the MA-22 class AB mono power amps.  They were awesome.  I liked them so much, I later upgraded them to 4ea of the MA-24 which were 30w class A units.  These sounded very good but truth be told, while I loved the physical design the MA-22 units actually sounded somewhat better driving my bi-amped Martin Logan Quests.

Just for lindisfarne...........whatcha gon be drivin wit dis amp nesto?

Seriously what speakers are you using? 300 watts is a ton and there are many good amps both tube and ss in the 30-100 watt range that are very affordable. And as always it's not just about watts! Power supply, overall design, are factors that are just if not more important.