What's the cheapest box to study for the Solaris tests with? The obvious answer is a T1000, but IIRC they have no CD/DVD and have to be jumpstarted. What's cheap that can run Solaris 11 and that doesn't require anything but itself?
A virtual machine with Solaris installed right on your latop/desktop computer.
Oracle VM VirtualBox
Oracle Solaris 11.3 Downloads - Oracle VM Templates
But you can't have a Sparc VM on a x86 box, right?
The T1000 is a rack-mounted server, and Solaris 11.x Sparc supports only such servers.
If you could use Solaris 10 then there are some fancy workstations available, such as the Sun Blade 1000 or 2000 or 1500.
According to Wikipedia the Sun Blade 1000 can even run Solaris 11 Express - I don't know if/how this is available from Oracle.
Precisely 
I have Solaris 11 installed on a laptop and am going to install on a beefy desktop, but I gotta know the ALOM stuff too.
Right, but what's the next server that will have a DVD and, preferably, a way to use a keyboard & monitor? T2000? Something else? I want cheap a lot more than I want tons of processing power or RAM or disk space...
Why a sparc server to practise for "Solaris tests"? The commands and all will be the same on x86 and a x86 VM... I'm certified for Solaris 10 and non of the questions have been sparc specific!
So, the cheapest and maybe easiest way might be a VM. Just my opinion of course and if the OP wants to buy a server, no objection from my side! Keep in mind that all T1/T2 and T2+ servers are very slow. From T3 on upwards the speed is good to work with.
ALOM is a little out of date. The newer systems all use ILOM or XSCF (for M-Series servers). As these are service processors for the actual server, there is not much to practise with. The documentation will help with that!
If you still want to buy hardware, a x86 server might be also usefull (like x4270 or so) because the also have an ILOM interface.
If you need to practise because you have to look after older Sun servers, be aware that there is a whole range of service processors for the older stuff...
RSC/SC/ALOM/ELOM and and and...