It looks as if a TI Voyage200 can do a single matrix of up to about 115x115. I haven't seen documentation on it yet, but a few experiments point to 10 bytes per element for arrays of floats (plus, of course, a few bytes of overhead). Unlike an HP48/49, the TI uses less storage if the array consists entirely of integers (that is, 4 bytes per element, plus a few bytes of overhead).
Arrays of complex numbers with floating point components take about 20 byes per (complex) element plus some overhead. So it looks as if the Voyage200 could do a single 81x81 matrix of all complex elements.
So far as I know, the TI-89, 92, 92+ and Voyage200 all have the same amount of RAM---they differ only in the amount of Flash memory, builtin apps, physical size, battery size (4xAA vs 4xAAA) and (in the case of the TI-89) display size.
--Mark