You can only add another MD1000. The MD3000 is a completely different storage solution that you could connect an MD1000 to (but not with data in place), and as far as I know it's not supported to daisy chain an MD1200 to an MD1000. The MD1000 is supported connected to a PERC5E or PERC6E, whereas the MD1200 requires (is supported) with a PERC H800.
Hello We have a MD1000 DAS SAS array which is populated by 300x15 disk. Configured 2 virtaul disk in RAID 5. Now we are looking to expand the array with another shelf. My questions are below. 1) Can we add another MD1000 shel on top of this box ? or it's possible to add another model n top of this ( lide MD 1220 or 3000?) 2) can we add 450 or 600 GB SAS Hard disk? 3) current connectivity to the Dell server is from Out port of MD1000 to In port of server.  So if we expand this array MD1000 IN port to new shelf out ?   
MD1000 DAS Expansion 