First off, the Trumpeter Chinese SPG kit is NOT a 2S3. It is a Chinese indigenous SPG based in part on knowledge from the 2S3. We had all HOPED it would be one, but no. It is a nice kit to build though.
The 2S1 is done by SKIF. It is older, but still in service. The 2S1M is the most current version. With new tracks, new turret, model point barrel, Eduard PE, and some scratchbuilt details, it comes out decent.
The D-30M, a towed version of the 2S1, is done by SKIF. Basic kit as well.
2S3 - noone has done one yet.
2S5 - Noone has done.
2S7- Done by Panzershop, this is the big 203mm. Will put you back $300-$350.
2S9 - Light weight 120mm artillery gun/mortar for Airborne units done by Eastern Express and more recently repopped by Alanger.
2S19 - Most Modern Russian Artillery. Noone has done a kit. ICM has had it listed in the past but nothing has ever surfaced. Panzershop threatens a expensive kit.
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2S4 - Massive SPG Mortar. Threatened by Panzershop
DANA - 152mm Wheeled SPG. Made by the Czech's and some are used by the Russians.
2S23 - BTR-80 based 120mm gun/mortar Wheeled SPG. Made by SP Designs and Capitan (are they even still in business?)
Rocket Artillery is something that the Russian's are also passionate about. ICM (and under other labels) does a BM24 MLRS.
The Smerch is a very modern MLRS based loosly on the same MAZ chassis as the SCUD-B. Noone has done this kit.
SP Designs also has a large number of MT-LBu based kits that are command, control, and aquisition vehicles with the artillery, like the Zoopark-1 Battelfield Radar, the 1V13 series of Artillery command and control vehicles, etc...
Russian srtillery philosophy is quite a bit different than Western Armies, so to try to get a exact "equivalent" is a bit of a misnomer...the Russian's are "tube heavy". They not only have larger organic mortar sections for their Infantry and Tank units, but they also believe in more overlap resulting in 4 main SPG tube types in service at the same time: 120mm, 122mm, 152mm and 203mm. For the same time period, for example, the US had 155mm and 203mm. Now it is only 155mm as a SPG. (Damned shame too!)
NOW...
If you want comparable artillery to go with a T-72, just build the SKIF 2S1. If you want to do a IDF/OIF setup, the 2S1 is an even better call since it was the main artillery piece of the Iraqi Army.
Also, right now T-72's are still in what was considered Catagory B units. These are primarily supported by similarly older artillery...2S1 and 2S3. Since there is no 2S3 for the 152mm "equivalent" to the 155mm M109A6 Paladin, this is your best bet.